Patent Publication Number: US-2022233923-A1

Title: Club head having balanced impact and swing performance characteristics

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 17/094,682 filed on Nov. 10, 2020, now U.S. Pat. No. 11,305,164 issued on Apr. 19, 2022, which is a continuation of U.S. patent application Ser. No. 16/523,828 filed on Jul. 26, 2019, now U.S. Pat. No. 10,828,541 issued Nov. 10, 2020, which is a continuation of U.S. patent application Ser. No. 15/815,547, filed on Nov. 16, 2017, now U.S. Pat. No. 10,434,381 issued on Oct. 8, 2019, which claims the benefit of U.S. Provisional Patent Appl. No. 62/469,911, filed on Mar. 10, 2017, U.S. Provisional Patent Appl. No. 62/449,403, filed on Jan. 23, 2017, U.S. Provisional Patent Appl. No. 62/423,878, filed on Nov. 18, 2016, and is a continuation in part of U.S. patent application Ser. No. 15/680,404, filed on Aug. 18, 2017, now U.S. Pat. No. 10,238,938, which is a continuation of U.S. patent application Ser. No. 14/836,739, filed on May 15, 2017, now U.S. Pat. No. 9,764,206, issued Sep. 19, 2017, which is a continuation of U.S. patent application Ser. No. 13/804,859, filed on Mar. 14, 2013, now U.S. Pat. No. 9,144,722, issued Sep. 29, 2015, the contents of all of which are incorporated fully herein by reference. 
    
    
     FIELD OF INVENTION 
     The present disclosure relates to golf club heads. In particular, the present disclosure is related to golf club heads having balanced impact and swing performance characteristics. 
     BACKGROUND 
     Various golf club head design parameters, such as volume, center of gravity position and moment of inertia, affect impact performance characteristics (e.g. spin, launch angle, speed, forgiveness) and swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact). Often, club head designs that improve impact performance characteristics can adversely affect swing performance characteristics (e.g. aerodynamic drag), or club head designs that improve swing performance characteristics can adversely affect impact performance characteristics. Accordingly, there is a need in the art for a club head having enhanced impact performance characteristics balanced with enhanced swing characteristics. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a golf club head according to one embodiment. 
         FIG. 2  is a side cross sectional view along line II-II of the golf club head in  FIG. 1 . 
         FIG. 3  is a bottom view of the golf club head in  FIG. 1 . 
         FIG. 4  is a side cross sectional view of the golf club head in  FIG. 1 . 
         FIG. 5  is an enlarged side cross sectional view of the golf club head in  FIG. 1 . 
         FIG. 6  is an enlarged side cross sectional view of the golf club head in  FIG. 1 . 
         FIG. 7  is a top view of the golf club head in  FIG. 1 . 
         FIG. 8  is a rear view of the golf club head in  FIG. 1 . 
         FIG. 9  is a side cross sectional view of the golf club head in  FIG. 1 . 
         FIG. 10A  illustrates a relationship between drag force and moment of inertia about the x-axis for various known golf club heads. 
         FIG. 10B  illustrates a relationship between drag force and moment of inertia about the y-axis for various known golf club heads. 
         FIG. 10C  illustrates a relationship between drag force and combined moment of inertia for various known golf club heads. 
         FIG. 11A  illustrates a relationship between drag force and combined moment of inertia of golf club heads described herein compared to known golf club heads. 
         FIG. 11B  illustrates a relationship between drag force and combined moment of inertia of golf club heads described herein compared to known golf club heads. 
         FIG. 11C  illustrates a relationship between drag force and combined moment of inertia of golf club heads described herein compared to known golf club heads. 
         FIG. 12  illustrates a relationship between drag force and club head center of gravity depth for various known golf club heads. 
         FIG. 13A  illustrates a relationship between drag force and club head center of gravity depth of golf club heads described herein compared to known golf club heads. 
         FIG. 13B  illustrates a relationship between drag force and club head center of gravity depth of golf club heads described herein compared to known golf club heads. 
         FIG. 13C  illustrates a relationship between drag force and club head center of gravity depth of golf club heads described herein compared to known golf club heads. 
         FIG. 14  illustrates a relationship between combined moment of inertia and club head center of gravity depth of golf club heads described herein compared to known golf club heads. 
         FIG. 15  is a front view of a golf club head according to another embodiment. 
         FIG. 16  is a side cross sectional view along line II-II of the golf club head in  FIG. 15 . 
         FIG. 17  is a bottom view of the golf club head in  FIG. 15 . 
         FIG. 18  is a side cross sectional view of the golf club head in  FIG. 15 . 
         FIG. 19  is an enlarged side cross sectional view of the golf club head in  FIG. 15 . 
         FIG. 20  is an enlarged side cross sectional view of the golf club head in  FIG. 15 . 
         FIG. 21  is a top view of the golf club head in  FIG. 15 . 
         FIG. 22  is a rear view of the golf club head in  FIG. 15 . 
         FIG. 23A  illustrates a relationship between drag force and moment of inertia about the x-axis for various known golf club heads. 
         FIG. 23B  illustrates a relationship between drag force and moment of inertia about the y-axis for various known golf club heads. 
         FIG. 23C  illustrates a relationship between drag force and combined moment of inertia for various known golf club heads. 
         FIG. 24A  illustrates a relationship between drag force and combined moment of inertia of golf club heads described herein compared to known golf club heads. 
         FIG. 24B  illustrates a relationship between drag force and combined moment of inertia of golf club heads described herein compared to known golf club heads. 
         FIG. 25  illustrates a relationship between drag force and club head center of gravity depth for various known golf club heads. 
         FIG. 26A  illustrates a relationship between drag force and club head center of gravity depth of golf club heads described herein compared to known golf club heads. 
         FIG. 26B  illustrates a relationship between drag force and club head center of gravity depth of golf club heads described herein compared to known golf club heads. 
         FIG. 27  illustrates a relationship between combined moment of inertia and club head center of gravity depth of golf club heads described herein compared to known golf club heads. 
     
    
    
     Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings. 
     For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the present disclosure. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present disclosure. The same reference numerals in different figures denote the same elements. 
     DETAILED DESCRIPTION 
     The golf club described below uses several relations that increases or maximizes the club head moment of inertia with a down and back CG position while simultaneously maintaining or reducing aerodynamic drag. Specifically, the golf club described herein has a low and back CG as specified. The golf club further has a high crown-to-sole moment of inertia (Ixx) and heel-to-toe moment of inertia (Iyy). A low and back CG, and increased moment of inertia are achieved by increasing discretionary weight or repositioning discretionary weight regions of the golf club head having maximum distances from the head CG. Thinning the crown and/or using optimized materials increases discretionary weighting. Using removable weights, a steep crown angle, or embedded weight allow for discretionary weight to be removed and placed at a maximum distance from the CG. 
     The golf club head described herein also has a reduced aerodynamic drag over golf club heads with a similar CG position and moment of inertia. Aerodynamic drag is reduced by maximizing the crown height while maintaining a low and back CG position. Transition profiles between the strikeface to crown, strikeface to sole, and/or crown to sole along the back end of the golf club head provides a means to reduce aerodynamic drag. The using of turbulators and strategic placement of hosel weight further reduce aerodynamic drag. 
     The golf club described below uses several relations that increases or maximizes the club head moment of inertia with a down and back CG position while simultaneously maintaining or reducing aerodynamic drag. Balancing these relationships of CG, moment of inertia and drag improve impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) and swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, swing speed). This balance is applicable to a driver-type club head, a fairway wood type club head and a hybrid-type club head. 
     The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms “include,” and “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, device, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, system, article, device, or apparatus. 
     The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the apparatus, methods, and/or articles of manufacture described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. 
     Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIGS. 1-3  illustrate a golf club head  100  having a body  102  and a strikeface  104 . The body  102  of the club head  100  includes a front end  108 , a back end  110  opposite the front end  108 , a crown  116 , a sole  118  opposite the crown  116 , a heel  120  and a toe  122  opposite the heel  120 . The body  102  further includes a skirt or trailing edge  128  located between and adjoining the crown  116  and the sole  118 , the skirt extending from near the heel  120  to near the toe  122  of the club head  100 . 
     In many embodiments, the club head  100  is a hollow body club head. In these embodiments, the body and strikeface can define an internal cavity of the golf club head  100 . In some embodiments, the body  102  can extend over the crown  116 , the sole  118 , the heel  120 , the toe  122 , the back end  110 , and the perimeter of the front end  108  of the club head  100 . In these embodiments, the body  102  defines an opening on the front end  108  of the club head  100  and the strikeface  104  is positioned within the opening to form the club head  100 . In other embodiments, the strikeface  104  can extend over the entire front end  108  of the club head and can include a return portion extending over at least one of the crown  116 , the sole  118 , the heel  120 , and the toe  122 . In these embodiments, the return portion of the strikeface  104  is coupled to the body  102  to form the club head  100 . 
     The strikeface  104  of the club head  100  comprises a first material. In many embodiments, the first material is a metal alloy, such as a titanium alloy, a steel alloy, an aluminum alloy, or any other metal or metal alloy. In other embodiments, the first material can comprise any other material, such as a composite, plastic, or any other suitable material or combination of materials. 
     The body  102  of the club head  100  comprises a second material. In many embodiments, the second material is a metal alloy, such as a titanium alloy, a steel alloy, an aluminum alloy, or any other metal or metal alloy. In other embodiments, the second material can comprise any other material, such as a composite, plastic, or any other suitable material or combination of materials. 
     The first and second material comprise a strength-to-weight ratio or specific strength measured as the ratio of the yield stress (σ y ) to the density (ρ) of the material (see Relation 1 below), and a strength-to-modulus ratio or specific flexibility measured as the ratio of the yield stress (σ y ) to the elastic modulus (E) of the material (see Relation 2 below). 
     
       
         
           
             
               
                 
                   
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                     Specific 
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                     Flexibility 
                   
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     As shown in  FIG. 1 , the club head  100  further comprises a hosel structure  130  and a hosel axis  132  extending centrally along a bore of the hosel structure  130 . In the present example, a hosel coupling mechanism of the club head  100  comprises the hosel structure  130  and a hosel sleeve  134 , where the hosel sleeve  134  can be coupled to an end of a golf shaft  136 . The hosel sleeve  134  can couple with the hosel structure  130  in a plurality of configurations, thereby permitting the golf shaft  136  to be secured to the hosel structure  130  at a plurality of angles relative to the hosel axis  132 . There can be other examples, however, where the shaft  136  can be non-adjustably secured to the hosel structure  130 . 
     The strikeface  104  of the club head  100  defines a geometric center  140 . In some embodiments, the geometric center  140  can be located at the geometric centerpoint of a strikeface perimeter  142 , and at a midpoint of face height  144 . In the same or other examples, the geometric center  140  also can be centered with respect to engineered impact zone  148 , which can be defined by a region of grooves  150  on the strikeface. As another approach, the geometric center of the strikeface can be located in accordance with the definition of a golf governing body such as the United States Golf Association (USGA). For example, the geometric center of the strikeface can be determined in accordance with Section 6.1 of the USGA&#39;s Procedure for Measuring the Flexibility of a Golf Clubhead (USGA-TPX3004, Rev. 1.0.0, May 1, 2008) (available at http://www.usga.org/equipment/testing/protocols/Procedure-For-Measuring-The-Flexibility-Of-A-Golf-Club-Head/) (the “Flexibility Procedure”). 
     The club head  100  further defines a loft plane  1010  tangent to the geometric center  140  of the strikeface  104 . The face height  144  can be measured parallel to loft plane  2270  between a top end of the strikeface perimeter  142  near the crown  116  and a bottom end of the strikeface perimeter  142  near the sole  118 . In these embodiments, the strikeface perimeter  142  can be located along the outer edge of the strikeface  104  where the curvature deviates from the bulge and/or roll of the strikeface  104 . 
     The geometric center  140  of the strikeface  104  further defines a coordinate system having an origin located at the geometric center  140  of the strikeface  104 , the coordinate system having an X′ axis  1052 , a Y′ axis  1062 , and a Z′ axis  1072 . The X′ axis  1052  extends through the geometric center  140  of the strikeface  104  in a direction from the heel  120  to the toe  122  of the club head  100 . The Y′ axis  1062  extends through the geometric center  140  of the strikeface  104  in a direction from the crown  116  to the sole  118  of the club head  100  and perpendicular to the X′ axis  1052 , and the Z′ axis  1072  extends through the geometric center  140  of the strikeface  104  in a direction from the front end  108  to the back end  110  of the club head  100  and perpendicular to the X′ axis  1052  and the Y′ axis  1062 . 
     The coordinate system defines an X′Y′ plane extending through the X′ axis  1052  and the Y′ axis  1062 , an X′Z′ plane extending through the X′ axis  1052  and the Z′ axis  1072 , and a Y′Z′ plane extending through the Y′ axis  1062  and the Z′ axis  1072 , wherein the X′Y′ plane, the X′Z′ plane, and the Y′Z′ plane are all perpendicular to one another and intersect at the origin of the coordinate system located at the geometric center  140  of the strikeface  104 . The X′Y′ plane extends parallel to the hosel axis  132  and is positioned at an angle corresponding to the loft angle of the club head  100  from the loft plane  1010 . Further the X′ axis  1052  is positioned at a 60 degree angle to the hosel axis  132  when viewed from a direction perpendicular to the X′Y′ plane. 
     In these or other embodiments, the club head  100  can be viewed from a front view ( FIG. 1 ) when the strikeface  104  is viewed from a direction perpendicular to the X′Y′ plane. Further, in these or other embodiments, the club head  100  can be viewed from a side view or side cross-sectional view ( FIG. 2 ) when the heel  120  is viewed from a direction perpendicular to the Y′Z′ plane. 
     The club head  100 ,  300  defines a depth  160 ,  360 , a length  162 ,  362 , and a height  164 , 364 . Referring to  FIG. 3 , the depth  160 ,  360  of the club head can be measured as the furthest extent of the club head  100 ,  300  from the front end  108 ,  308  to the back end  110 ,  310 , in a direction parallel to the Z′ axis  1072 . 
     The length  162  of the club head  100  can be measured as the furthest extent of the club head  100  from the heel  120  to the toe  122 , in a direction parallel to the X′ axis  1052 , when viewed from the front view ( FIG. 1 ). In many embodiments, the length  162  of the club head  100  can be measured according to a golf governing body such as the United States Golf Association (USGA). For example, the length  162  of the club head  100  can be determined in accordance with the USGA&#39;s Procedure for Measuring the Club Head Size of Wood Clubs (USGA-TPX3003, Rev. 1.0.0, Nov. 21, 2003) (available at https://www.usga.org/content/dam/usga/pdf/Equipment/TPX3003-procedure-for-measuring-the-club-head-size-of-wood-clubs.pdf) (the “Procedure for Measuring the Club Head Size of Wood Clubs”). 
     The height  164  of the club head  100  can be measured as the furthest extend of the club head  100  from the crown  116  to the sole  118 , in a direction parallel to the Y′ axis  1062 , when viewed from the front view ( FIG. 1 ). In many embodiments, the height  164  of the club head  100  can be measured according to a golf governing body such as the United States Golf Association (USGA). For example, the height  164  of the club head  100  can be determined in accordance with the USGA&#39;s Procedure for Measuring the Club Head Size of Wood Clubs (USGA-TPX3003, Rev. 1.0.0, Nov. 21, 2003) (available at https://www.usga.org/content/dam/usga/pdf/Equipment/TPX3003-procedure-for-measuring-the-club-head-size-of-wood-clubs.pdf) (the “Procedure for Measuring the Club Head Size of Wood Clubs”). 
     As shown in  FIGS. 1 and 2 , the club head  100  further comprises a head center of gravity (CG)  170  and a head depth plane  1040  extending through the geometric center  140  of the strikeface  104 , perpendicular to the loft plane  1010 , in a direction from the heel  120  to the toe  122  of the club head  100 . In many embodiments, the head CG  170  is located at a head CG depth from the X′Y′ plane, measured in a direction perpendicular to the X′Y′ plane. In some embodiments, the head CG  170  can be located at a head CG depth  172  from the loft plane  1010 , measured in a direction perpendicular to the loft plane. The head CG  170  is further located at a head CG height  174  from the head depth plane  1040 , measured in a direction perpendicular to the head depth plane  1040 . Further, the head CG height  174  is measured as the offset distance from the head depth plane  1040  in a direction perpendicular to the head depth plane  1040  toward the crown  116  or toward the sole  118 . In many embodiments, the head CG height  174  is positive when the head CG is located above the head depth plane  1040  (i.e. between the head depth plane  1040  and the crown  116 ), and the head CG height  174  is negative with the head CG is located below the head depth plane  1040  (i.e. between the head depth plane  1040  and the sole  118 ). In some embodiments, the absolute value of the head CG height  174  can describe a head CG positioned above or below the head depth plane  1040  (i.e. between the head depth plane  1040  and the crown  116  or between the head depth plane  1040  and the sole  118 ). In many embodiments, the head CG  170  is strategically positioned toward the sole  118  and back end  110  of the club head  100  based on various club head parameters, such as volume and loft angle, as described below. Further, in many embodiments, the head CG  170  is strategically positioned toward the sole  118  and back end  110  of the club head  100  in combination with reduced aerodynamic drag. 
     The head CG  170  defines an origin of a coordinate system having an x-axis  1050 , a y-axis  1060 , and a z-axis  1070 . The y-axis  1060  extends through the head CG  170  from the crown  116  to the sole  118 , parallel to the hosel axis  132  when viewed from the side view and at a 30 degree angle from the hosel axis  132  when viewed from the front view. The x-axis  1050  extends through the head CG  170  from the heel  120  to the toe  122  and perpendicular to the y-axis  1060  when viewed from a front view and parallel to the X′Y′ plane. The z-axis  1070  extends through the head CG  170  from the front end  108  to the back end  110  and perpendicular to the x-axis  1050  and the y-axis. In many embodiments, the x-axis  1050  extends through the head CG  170  from the heel  120  to the toe  122  and parallel to the X′ axis  1052 , the y-axis  1060  through the head CG  170  from the crown  116  to the sole  118  parallel to the Y′ axis  1062 , and the z-axis  1070  extends through the head CG  170  from the front end  108  to the back end  110  and parallel to the Z′ axis  1072 . 
     The club head  100  further comprises a moment of inertia about the x-axis I xx  (i.e. crown-to-sole moment of inertia), and a moment of inertia about the y-axis I yy  (i.e. heel-to-toe moment of inertia). In many embodiments, the crown-to-sole moment of inertia I xx  and the heel-to-toe moment of inertia I yy  are increased or maximized based on various club head parameters, such as volume and loft angle, as described in further detail below. Further, in many embodiments, the crown-to-sole moment of inertia I xx  and the heel-to-toe moment of inertia I yy  are increased or maximized in combination with reduced aerodynamic drag. 
     Various embodiments of the club head having varied loft angles and volumes are described below. Other embodiments can include club heads having loft angles or volumes different than the loft angles and volumes described herein. 
     I. High Volume Driver-Type Club Head 
     According to one example, a golf club head  300  comprises a high volume and a low loft angle. In many embodiments, the golf club head  300  comprises a driver-type club head. In other embodiments, the golf club head  300  can comprise any type of golf club head having a loft angle and volume as described herein. In many embodiments, club head  300  comprises the same or similar parameters as club head  100 , wherein the parameters are described with the club head  100  reference numbers plus  200 . 
     In many embodiments, the loft angle of the club head  300  is less than approximately 16 degrees, less than approximately 15 degrees, less than approximately 14 degrees, less than approximately 13 degrees, less than approximately 12 degrees, less than approximately 11 degrees, or less than approximately 10 degrees. Further, in many embodiments, the volume of the club head  300  is greater than approximately 400 cc, greater than approximately 425 cc, greater than approximately 450 cc, greater than approximately 475 cc, greater than approximately 500 cc, greater than approximately 525 cc, greater than approximately 550 cc, greater than approximately 575 cc, greater than approximately 600 cc, greater than approximately 625 cc, greater than approximately 650 cc, greater than approximately 675 cc, or greater than approximately 700 cc. In some embodiments, the volume of the club head can be approximately 400 cc-600 cc, 445 cc-485 cc, 425 cc-500 cc, approximately 500 cc-600 cc, approximately 500 cc-650 cc, approximately 550 cc-700 cc, approximately 600 cc-650 cc, approximately 600 cc-700 cc, or approximately 600 cc-800 cc. 
     In many embodiments, the length  362  of the club head  300  is greater than 4.85 inches. In other embodiments, the length  362  of the club head  300  is greater than 4.5 inches, greater than 4.6 inches, greater than 4.7 inches, greater than 4.8, greater than 4.9 inches, or greater than 5.0 inches. For example, in some embodiments, the length  362  of the club head  300  can be between 4.6-5.0 inches, between 4.7-5.0 inches, between 4.8-5.0 inches, between 4.85-5.0 inches, or between 4.9-5.0 inches. 
     In many embodiments, the depth  360  of the club head  300  is at least 0.70 inches less than the length  362  of the club head  300 . In many embodiments, the depth  360  of the club head  300  is greater than 4.75 inches. In other embodiments, the depth  360  of the club head  300  is greater than 4.5 inches, greater than 4.6 inches, greater than 4.7 inches, greater than 4.8, greater than 4.9 inches, or greater than 5.0 inches. For example, in some embodiments, the depth  360  of the club head  300  can be between 4.6-5.0 inches, between 4.7-5.0 inches, between 4.75-5.0 inches, between 4.8-5.0 inches, or between 4.9-5.0 inches. 
     In many embodiments, the height  364  of the club head  300  is less than approximately 2.8 inches. In other embodiments, the height  364  of the club head  300  is less than 3.0 inches, less than 2.9 inches, less than 2.8 inches, less than 2.7, or less than 2.6 inches. For example, in some embodiments, the height  364  of the club head  300  can be between 2.0-2.8 inches, between 2.2-2.8 inches, between 2.5-2.8 inches, or between 2.5-3.0 inches. Further, in many embodiments, the face height  344  of the club head  300  can be approximately 1.3 inches (33 mm) to approximately 2.8 inches (71 mm). Further still, in many embodiments, the club head  300  can comprise a mass between 185 grams and 225 grams. 
     The club head  300  further comprises a balance of various additional parameters, such as head CG position, club head moment of inertia, and aerodynamic drag, to provide both improved impact performance characteristics (e.g. spin, launch angle, speed, forgiveness) and swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact). In many embodiments, the balance of parameters described below provides improved impact performance while maintaining or improving swing performance characteristics. Further, in many embodiments, the balance of parameters described below provides improved swing performance characteristics while maintaining or improving impact performance characteristics. 
     A. Center of Gravity Position and Moment of Inertia 
     In many embodiments, a low and back club head CG and increased moment of inertia can be achieved by increasing discretionary weight and repositioning discretionary weight in regions of the club head having maximized distances from the head CG. Increasing discretionary weight can be achieved by thinning the crown and/or using optimized materials, as described above relative to the head CG position. Repositioning discretionary weight to maximize the distance from the head CG can be achieved using removable weights, embedded weights, or a steep crown angle, as described above relative to the head CG position. 
     In many embodiments, the club head  300  comprises a crown-to-sole moment of inertia I xx  greater than approximately 3000 g·cm 2 , greater than approximately 3250 g·cm 2 , greater than approximately 3500 g·cm 2 , greater than approximately 3750 g·cm 2 , greater than approximately 4000 g·cm 2 , greater than approximately 4250 g·cm 2 , greater than approximately 4500 g·cm 2 , greater than approximately 4750 g·cm 2 , greater than approximately 5000 g·cm 2 , greater than approximately 5250 g·cm 2 , greater than approximately 5500 g·cm 2 , greater than approximately 5750 g·cm 2 , greater than approximately 6000 g·cm 2 , greater than approximately 6250 g·cm 2 , greater than approximately 6500 g·cm 2 , greater than approximately 6750 g·cm 2 , or greater than approximately 7000 g·cm 2 . 
     In many embodiments, the club head  300  comprises a heel-to-toe moment of inertia I yy  greater than approximately 5000 g·cm 2 , greater than approximately 5250 g·cm 2 , greater than approximately 5500 g·cm 2 , greater than approximately 5750 g·cm 2 , greater than approximately 6000 g·cm 2 , greater than approximately 6250 g·cm 2 , greater than approximately 6500 g·cm 2 , greater than approximately 6750 g·cm 2 , or greater than approximately 7000 g·cm 2 . 
     In many embodiments, the club head  300  comprises a combined moment of inertia (i.e. the sum of the crown-to-sole moment of inertia I xx  and the heel-to-toe moment of inertia I yy ) greater than 8000 g·cm 2 , greater than 8500 g·cm 2 , greater than 8750 g·cm 2 , greater than 9000 g·cm 2 , greater than 9250 g·cm 2 , greater than 9500 g·cm 2 , greater than 9750 g·cm 2 , greater than 10000 g·cm 2 , greater than 10250 g·cm 2 , greater than 10500 g·cm 2 , greater than 10750 g·cm 2 , greater than 11000 g·cm 2 , greater than 11250 g·cm 2 , greater than 11500 g·cm 2 , greater than 11750 g·cm 2 , or greater than 12000 g·cm 2 , greater than 12500 g·cm 2 , greater than 1300 g·cm 2 , greater than 13500 g·cm 2 , or greater than 1400 g·cm 2 . 
     In many embodiments, the club head  300  comprises a head CG height  374  less than approximately 0.20 inches, less than approximately 0.15 inches, less than approximately 0.10 inches, less than approximately 0.09 inches, less than approximately 0.08 inches, less than approximately 0.07 inches, less than approximately 0.06 inches, or less than approximately 0.05 inches. Further, in many embodiments, the club head  300  comprises a head CG height  374  having an absolute value less than approximately 0.20 inches, less than approximately 0.15 inches, less than approximately 0.10 inches, less than approximately 0.09 inches, less than approximately 0.08 inches, less than approximately 0.07 inches, less than approximately 0.06 inches, or less than approximately 0.05 inches. 
     In many embodiments, the club head  300  comprises a head CG depth  372  greater than approximately 1.2 inches, greater than approximately 1.3 inches, greater than approximately 1.4 inches, greater than approximately 1.5 inches, greater than approximately 1.6 inches, greater than approximately 1.7 inches, greater than approximately 1.8 inches, greater than approximately 1.9 inches, or greater than approximately 2.0 inches. 
     In some embodiments, the club head  300  can comprise a first performance characteristic less than or equal to 0.56, wherein the first performance characteristic is defined as a ratio between (a) the difference between 72 mm and the face height  344 , and (b) the head CG depth  372 . In these or other embodiments, the club head  300  can comprise a second performance characteristic greater than or equal to 425 cc, wherein the second performance characteristic is defined as the sum of (a) the volume of the club head  300 , and (b) a ratio between the head CG depth  372  and the absolute value of the head CG height  374 . In some embodiments, the second performance characteristic can be greater than or equal to 450 cc, greater than or equal to 475 cc, greater than or equal to 490 cc, greater than or equal to 495 cc, greater than or equal to 500 cc, greater than or equal to 505 cc, or greater than or equal to 510 cc. 
     The club head  300  having the reduced head CG height  374  can reduce the backspin of a golf ball on impact compared to a similar club head having a higher head CG height. In many embodiments, reduced backspin can increase both ball speed and travel distance for improve club head performance. Further, the club head  300  having the increased head CG depth  372  can increase the heel-to-toe moment of inertia compared to a similar club head having a head CG depth closer to the strikeface. Increasing the heel-to-toe moment of inertia can increase club head forgiveness on impact to improve club head performance. Further still, the club head  300  having the increased head CG depth  172  can increase launch angle of a golf ball on impact by increasing the dynamic loft of the club head at delivery, compared to a similar club head having a head CG depth closer to the strikeface. 
     The head CG height  374  and/or head CG depth  372  can be achieved by reducing weight of the club head in various regions, thereby increasing discretionary weight, and repositioning discretionary weight in strategic regions of the club head to shift the head CG lower and farther back. Various means to reduce and reposition club head weight are described below. 
     i. Thin Regions 
     In some embodiments, the head CG height  374  and/or head CG depth  372  can be achieved by thinning various regions of the club head  300  to remove excess weight. Removing excess weight results in increased discretionary weight that can be strategically repositioned to regions of the club head  300  to achieve the desired low and back club head CG position. 
     In many embodiments, the club head  300  can have one or more thin regions  376 . The one or more thin regions  376  can be positioned on the strikeface  304 , the body  302 , or a combination of the strikeface  304  and the body  302  (see  FIG. 7 ). Further, the one or more thin regions  376  can be positioned on any region of the body  302 , including the crown  316 , the sole  318 , the heel  320 , the toe  322 , the front end  308 , the back end  310 , the skirt  328 , or any combination of the described positions. For example, in some embodiments, the one or more thin regions  376  can be positioned on the crown  316 . For further example, the one or more thin regions  376  can be positioned on a combination of the strikeface  304  and the crown  306 . For further example, the one or more thin regions  376  can be positioned on a combination of the strikeface  304 , the crown  316 , and the sole  318 . For further example, the entire body  302  and/or the entire strikeface  304  can comprise a thin region  376 . 
     In embodiments where one or more thin regions  376  are positioned on the strikeface  304 , the thickness of the strikeface  304  can vary defining a maximum strikeface thickness and a minimum strikeface thickness. In these embodiments, the minimum strikeface thickness can be less than 0.10 inches, less than 0.09 inches, less than 0.08 inches, less than 0.07 inches, less than 0.06 inches, less than 0.05 inches, less than 0.04 inches, or less than 0.03 inches. In these or other embodiments, the maximum strikeface thickness can be less than 0.20 inches, less than 0.19 inches, less than 0.18 inches, less than 0.17 inches, less than 0.16 inches, less than 0.15 inches, less than 0.14 inches, less than 0.13 inches, less than 0.12 inches, less than 0.11 inches, or less than 0.10 inches. 
     In embodiments where one or more thin regions  376  are positioned on the body  302 , the thin regions can comprise a thickness less than approximately 0.020 inches. In other embodiments, the thin regions comprise a thickness less than 0.025 inches, less than 0.020 inches, less than 0.019 inches, less than 0.018 inches, less than 0.017 inches, less than 0.016 inches, less than 0.015 inches, less than 0.014 inches, less than 0.013 inches, less than 0.012 inches, or less than 0.010 inches. For example, the thin regions can comprise a thickness between approximately 0.010-0.025 inches, between approximately 0.013-0.020 inches, between approximately 0.014-0.020 inches, between approximately 0.015-0.020 inches, between approximately 0.016-0.020 inches, between approximately 0.017-0.020 inches, or between approximately 0.018-0.020 inches. 
     In the illustrated embodiment, the thin regions  376  vary in shape and position and cover approximately 25% of the surface area of club head  300 . In other embodiments, the thin regions can cover approximately 20-30%, approximately 15-35%, approximately 15-25%, approximately 10-25%, approximately 15-30%, or approximately 20-50% of the surface area of club head  900 . Further, in other embodiments, the thin regions can cover up to 5%, up to 10%, up to 15%, up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, or up to 50% of the surface area of club head  300 . 
     In many embodiments, the crown  316  can comprise one or more thin regions  376 , such that approximately 51% of the surface area of the crown  316  comprises thin regions  376 . In other embodiments, the crown  316  can comprise one or more thin regions  376 , such that up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, up to 50%, up to 55%, up to 60%, up to 65%, up to 70%, up to 75%, up to 80%, up to 85%, or up to 90% of the crown  316  comprises thin regions  376 . For example, in some embodiments, approximately 40-60% of the crown  316  can comprise thin regions  376 . For further example, in other embodiments, approximately 50-100%, approximately 40-80%, approximately 35-65%, approximately 30-70%, or approximately 25-75% of the crown  316  can comprise thin regions  376 . In some embodiments, the crown  316  can comprise one or more thin regions  376 , wherein each of the one or more thin regions  376  become thinner in a gradient fashion. In this exemplary embodiment, the one or more thin regions  376  of the crown  316  extend in a heel-to-toe direction, and each of the one or more thin regions  376  decrease in thickness in a direction from the strikeface  304  toward the back end  310 . 
     In many embodiments, the sole  318  can comprise one or more thin regions  376 , such that approximately 64% of the surface area of the sole  318  comprises thin regions  376 . In other embodiments, the sole  318  can comprise one or more thin regions  376 , such that up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, up to 50%, up to 55%, up to 60%, up to 65%, up to 70%, up to 75%, up to 80%, up to 85%, or up to 90% of the sole  318  comprises thin regions  376 . For example, in some embodiments, approximately 40-60% of the sole  318  can comprise thin regions  376 . For further example, in other embodiments, approximately 50-100%, approximately 40-80%, approximately 35-65%, approximately 30-70%, or approximately 25-75% of the sole  318  can comprise thin regions  376 . 
     The thinned regions  376  can comprise any shape, such as circular, triangular, square, rectangular, ovular, or any other polygon or shape with at least one curved surface. Further, one or more thinned regions  376  can comprise the same shape as, or a different shape than the remaining thinned regions. 
     In many embodiments, club head  100  having thin regions can be manufacturing using centrifugal casting. In these embodiments, centrifugal casting allows the club head  300  to have thinner walls than a club head manufactured using conventional casting. In other embodiments, portions of the club head  300  having thin regions can be manufactured using other suitable methods, such as stamping, forging, or machining. In embodiments where portions of the club head  300  having thin regions are manufactured using stamping, forging, or machining, the portions of the club head  300  can be coupled using epoxy, tape, welding, mechanical fasteners, or other suitable methods. 
     ii. Optimized Materials 
     In some embodiments, the strikeface  304  and/or the body  302  can comprise an optimized material having increased specific strength and/or increased specific flexibility. The specific flexibility is measured as a ratio of the yield strength to the elastic modulus of the optimized material. Increasing specific strength and/or specific flexibility can allow portions of the club head to be thinned, while maintaining durability. 
     In some embodiments, the first material of the strikeface  304  can be an optimized material, as described in U.S. Provisional Patent Appl. No. 62/399,929, entitled “Golf Club Heads with Optimized Material Properties.” In these or other embodiments, the first material comprising an optimized titanium alloy can have a specific strength greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 910,000 PSI/lb/in 3  (227 MPa/g/cm 3 ), greater than or equal to approximately 920,000 PSI/lb/in 3  (229 MPa/g/cm 3 ), greater than or equal to approximately 930,000 PSI/lb/in 3  (232 MPa/g/cm 3 ), greater than or equal to approximately 940,000 PSI/lb/in 3  (234 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 960,000 PSI/lb/in 3  (239 MPa/g/cm 3 ), greater than or equal to approximately 970,000 PSI/lb/in 3  (242 MPa/g/cm 3 ), greater than or equal to approximately 980,000 PSI/lb/in 3  (244 MPa/g/cm 3 ), greater than or equal to approximately 990,000 PSI/lb/in 3  (247 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), greater than or equal to approximately 1,100,000 PSI/lb/in 3  (274 MPa/g/cm 3 ), or greater than or equal to approximately 1,150,000 PSI/lb/in 3  (286 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the first material comprising an optimized titanium alloy can have a specific flexibility greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0091, greater than or equal to approximately 0.0092, greater than or equal to approximately 0.0093, greater than or equal to approximately 0.0094, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0096, greater than or equal to approximately 0.0097, greater than or equal to approximately 0.0098, greater than or equal to approximately 0.0099, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, or greater than or equal to approximately 0.0120. 
     In these or other embodiments, the first material comprising an optimized steel alloy can have a specific strength greater than or equal to approximately 650,000 PSI/lb/in 3  (162 MPa/g/cm 3 ), greater than or equal to approximately 700,000 PSI/lb/in 3  (174 MPa/g/cm 3 ), greater than or equal to approximately 750,000 PSI/lb/in 3  (187 MPa/g/cm 3 ), greater than or equal to approximately 800,000 PSI/lb/in 3  (199 MPa/g/cm 3 ), greater than or equal to approximately 810,000 PSI/lb/in 3  (202 MPa/g/cm 3 ), greater than or equal to approximately 820,000 PSI/lb/in 3  (204 MPa/g/cm 3 ), greater than or equal to approximately 830,000 PSI/lb/in 3  (207 MPa/g/cm 3 ), greater than or equal to approximately 840,000 PSI/lb/in 3  (209 MPa/g/cm 3 ), greater than or equal to approximately 850,000 PSI/lb/in 3  (212 MPa/g/cm 3 ), greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), greater than or equal to approximately 1,100,000 PSI/lb/in 3  (274 MPa/g/cm 3 ), greater than or equal to approximately 1,115,000 PSI/lb/in 3  (278 MPa/g/cm 3 ), or greater than or equal to approximately 1,120,000 PSI/lb/in 3  (279 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the first material comprising an optimized steel alloy can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0065, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, greater than or equal to approximately 0.0120, greater than or equal to approximately 0.0125, greater than or equal to approximately 0.0130, greater than or equal to approximately 0.0135, greater than or equal to approximately 0.0140, greater than or equal to approximately 0.0145, or greater than or equal to approximately 0.0150. 
     In these embodiments, the increased specific strength and/or increased specific flexibility of the optimized first material allow the strikeface  304 , or portions thereof, to be thinned, as described above, while maintaining durability. Thinning of the strikeface  304  can reduce the weight of the strikeface, thereby increasing discretionary weight to be strategically positioned in other areas of the club head  300  to position the head CG low and back and/or increase the club head moment of inertia. 
     In some embodiments, the second material of the body  302  can be an optimized material, as described in U.S. Provisional Patent Appl. No. 62/399,929, entitled “Golf Club Heads with Optimized Material Properties.” In these or other embodiments, the second material comprising an optimized titanium alloy can have a specific strength greater than or equal to approximately 730,500 PSI/lb/in 3  (182 MPa/g/cm 3 ). For example, the specific strength of the optimized titanium alloy can be greater than or equal to approximately 650,000 PSI/lb/in 3  (162 MPa/g/cm 3 ), greater than or equal to approximately 700,000 PSI/lb/in 3  (174 MPa/g/cm 3 ), greater than or equal to approximately 750,000 PSI/lb/in 3  (187 MPa/g/cm 3 ), greater than or equal to approximately 800,000 PSI/lb/in 3  (199 MPa/g/cm 3 ), greater than or equal to approximately 850,000 PSI/lb/in 3  (212 MPa/g/cm 3 ), greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), or greater than or equal to approximately 1,100,000 PSI/lb/in 3  (272 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the second material comprising an optimized titanium alloy can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0065, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, or greater than or equal to approximately 0.0120. 
     In these or other embodiments, the second material comprising an optimized steel can have a specific strength greater than or equal to approximately 500,000 PSI/lb/in 3  (125 MPa/g/cm 3 ), greater than or equal to approximately 510,000 PSI/lb/in 3  (127 MPa/g/cm 3 ), greater than or equal to approximately 520,000 PSI/lb/in 3  (130 MPa/g/cm 3 ), greater than or equal to approximately 530,000 PSI/lb/in 3  (132 MPa/g/cm 3 ), greater than or equal to approximately 540,000 PSI/lb/in 3  (135 MPa/g/cm 3 ), greater than or equal to approximately 550,000 PSI/lb/in 3  (137 MPa/g/cm 3 ), greater than or equal to approximately 560,000 PSI/lb/in 3  (139 MPa/g/cm 3 ), greater than or equal to approximately 570,000 PSI/lb/in 3  (142 MPa/g/cm 3 ), greater than or equal to approximately 580,000 PSI/lb/in 3  (144 MPa/g/cm 3 ), greater than or equal to approximately 590,000 PSI/lb/in 3  (147 MPa/g/cm 3 ), greater than or equal to approximately 600,000 PSI/lb/in 3  (149 MPa/g/cm 3 ), greater than or equal to approximately 625,000 PSI/lb/in 3  (156 MPa/g/cm 3 ), greater than or equal to approximately 675,000 PSI/lb/in 3  (168 MPa/g/cm 3 ), greater than or equal to approximately 725,000 PSI/lb/in 3  (181 MPa/g/cm 3 ), greater than or equal to approximately 775,000 PSI/lb/in 3  (193 MPa/g/cm 3 ), greater than or equal to approximately 825,000 PSI/lb/in 3  (205 MPa/g/cm 3 ), greater than or equal to approximately 875,000 PSI/lb/in 3  (218 MPa/g/cm 3 ), greater than or equal to approximately 925,000 PSI/lb/in 3  (230 MPa/g/cm 3 ), greater than or equal to approximately 975,000 PSI/lb/in 3  (243 MPa/g/cm 3 ), greater than or equal to approximately 1,025,000 PSI/lb/in 3  (255 MPa/g/cm 3 ), greater than or equal to approximately 1,075,000 PSI/lb/in 3  (268 MPa/g/cm 3 ), or greater than or equal to approximately 1,125,000 PSI/lb/in 3  (280 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the second material comprising an optimized steel can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0062, greater than or equal to approximately 0.0064, greater than or equal to approximately 0.0066, greater than or equal to approximately 0.0068, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0072, greater than or equal to approximately 0.0076, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0084, greater than or equal to approximately 0.0088, greater than or equal to approximately 0.0092, greater than or equal to approximately 0.0096, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, greater than or equal to approximately 0.0120, greater than or equal to approximately 0.0125, greater than or equal to approximately 0.0130, greater than or equal to approximately 0.0135, greater than or equal to approximately 0.0140, greater than or equal to approximately 0.0145, or greater than or equal to approximately 0.0150. 
     In these embodiments, the increased specific strength and/or increased specific flexibility of the optimized second material allow the body  302 , or portions thereof, to be thinned, while maintaining durability. Thinning of the body can reduce club head weight, thereby increasing discretionary weight to be strategically positioned in other areas of the club head  300  to position the head CG low and back and/or increase the club head moment of inertia. 
     iii. Removable Weights 
     In some embodiments, the club head  300  can include one or more weight structures  380  comprising one or more removable weights  382 . The one or more weight structures  380  and/or the one or more removable weights  382  can be located towards the sole  318  and towards the back end  310 , thereby positioning the discretionary weight on the sole  318  and near the back end  310  of the club head  300  to achieve a low and back head CG position. In many embodiments, the one or more weight structures  380  removably receive the one or more removable weights  382 . In these embodiments, the one or more removable weights  382  can be coupled to the one or more weight structures  380  using any suitable method, such as a threaded fastener, an adhesive, a magnet, a snap fit, or any other mechanism capable of securing the one or more removable weights to the one or more weight structures. 
     The weight structure  380  and/or removable weight  382  can be located relative to a clock grid  2000 , which can be aligned with respect to the strikeface  304  when viewed from a top or bottom view ( FIG. 3 ). The clock grid comprises at least a 12 o&#39;clock ray, a 3 o&#39;clock ray, a 4 o&#39;clock ray, a 5 o&#39;clock ray, a 6 o&#39;clock ray, a 7 o&#39;clock ray, a 8 o&#39;clock ray, and a 9 o&#39;clock ray. For example, the clock grid  2000  comprises a 12 o&#39;clock ray  2012 , which is aligned with the geometric center  340  of the strikeface  304 . The 12 o&#39;clock ray  2012  is orthogonal to the X′Y′ plane. Clock grid  2000  can be centered along 12 o&#39;clock ray  2012 , at a midpoint between the front end  308  and back end  310  of the club head  300 . In the same or other examples, a clock grid centerpoint  2010  can be centered proximate to a geometric centerpoint of golf club head  300  when viewed from a bottom view ( FIG. 3 ). The clock grid  2000  also comprises a 3 o&#39;clock ray  2003  extending towards the heel  320 , and a 9 o&#39;clock ray  2009  extending towards the toe  322  of the club head  300 . 
     A weight perimeter  384  of the weight structure  380  is located in the present embodiment towards the back end  310 , at least partially bounded between a 4 o&#39;clock ray  2004  and 8 o&#39;clock ray  2008  of clock grid  2000 , while a weight center  386  of a removable weight  382  positioned within the weight structure  380  is located between a 5 o&#39;clock ray  2005  and a 7 o&#39;clock ray  2007 . In examples such as the present one, the weight perimeter  384  is fully bounded between the 4 o&#39;clock ray  2004  and the 8 o&#39;clock ray  2008 . Although the weight perimeter  384  is defined external to the club head  300  in the present example, there can be other examples where the weight perimeter  384  may extend into an interior of, or be defined within, the club head  300 . In some examples, the location of the weight structure  380  can be established with respect to a broader area. For instance, in such examples, the weight perimeter  384  of the weight structure  380  can be located towards the back end  310 , at least partially bounded between the 4 o&#39;clock ray  2004  and 9 o&#39;clock ray  2009  of the clock grid  2000 , while the weight center  386  can be located between the 5 o&#39;clock ray  2005  and 8 o&#39;clock ray  2008 . 
     In the present example, the weight structure  380  protrudes from the external contour of the sole  318 , and is thus at least partially external to allow for greater adjustment of the head CG  370 . In some examples, the weight structure  380  can comprise a mass of approximately 2 grams to approximately 50 grams, and/or a volume of approximately 1 cc to approximately 30 cc. In other examples, the weight structure  380  can remain flush with the external contour of the body  302 . 
     In many embodiments, the removable weight  382  can comprise a mass of approximately 0.5 grams to approximately 30 grams, and can be replaced with one or more other similar removable weights to adjust the location of the head CG  370 . In the same or other examples, the weight center  386  can comprise at least one of a center of gravity of the removable weight  382 , and/or a geometric center of removable weight  382 . 
     iv. Embedded Weights 
     In some embodiments, the club head  300  can include one or more embedded weights  383  to position the discretionary weight on the sole  318 , in the skirt  328 , and/or near the back end  310  of the club head  300  to achieve a low and back head CG position. In many embodiments, the one or more embedded weights  383  are permanently fixed to or within the club head  300 . In these embodiments, the embedded weight  383  can be similar to the high density metal piece (HDMP) described in U.S. Provisional Patent Appl. No. 62/372,870, entitled “Embedded High Density Casting.” 
     In many embodiments, the one or more embedded weights  383  are positioned near the back end  310  of the club head  300 . For example, a weight center  387  of the embedded weight  383  can be located between the 5 o&#39;clock ray  2005  and 7 o&#39;clock ray  2007 , or between the 5 o&#39;clock ray  2005  and 8 o&#39;clock ray  2008  of the clock grid  2000 . In many embodiments, the one or more embedded weights  383  can be positioned on the skirt  328  and near the back end  310  of the club head  300 , on the sole  318  and near the back end  310  of the club head  300 , or on the skirt  328  and the sole  318  near the back end  310  of the club head  300 . 
     In many embodiments, the weight center  387  of the one or more embedded weights  383  is positioned within 0.10 inches, within 0.20 inches, within 0.30 inches, within 0.40 inches, within 0.50 inches, within 0.60 inches, within 0.70 inches, within 0.80 inches, within 0.90 inches, within 1.0 inches, within 1.1 inches, within 1.2 inches, within 1.3 inches, within 1.4 inches, or within 1.5 inches of a perimeter of the club head  300  when viewed from a top or bottom view ( FIG. 3 ). In these embodiments, the proximity of the embedded weight  383  to the perimeter of the club head  300  can maximize the low and back head CG position, the crown-to-sole moment of inertia I xx , and/or the heel-to-toe moment of inertia I yy . 
     In many embodiments, the weight center  387  of the one or more embedded weights  383  is positioned at a distance from the head CG  370  greater than 1.6 inches, greater than 1.7 inches, greater than 1.8 inches, greater than 1.9 inches, greater than 2.0 inches, greater than 2.1 inches, greater than 2.2 inches, greater than 2.3 inches, greater than 2.4 inches, greater than 2.5 inches, greater than 2.6 inches, greater than 2.7 inches, greater than 2.8 inches, greater than 2.9 inches, or greater than 3.0 inches. 
     In many embodiments, the weight center  387  of the one or more embedded weights  383  is positioned at a distance from the geometric center  340  of the strikeface  304  greater than 4.0 inches, greater than 4.1 inches, greater than 4.2 inches, greater than 4.3 inches, greater than 4.4 inches, greater than 4.5 inches, greater than 4.6 inches, greater than 4.7 inches, greater than 4.8 inches, greater than 4.9 inches, or greater than 5.0 inches. 
     In many embodiments, the one or more embedded weights  383  can comprise a mass between 3.0-50 grams. For example, in some embodiments, the one or more embedded weights  383  can comprise a mass between 3.0-25 grams, between 10-30 grams, between 20-40 grams, or between 30-50 grams. In embodiments where the one or more embedded weights  383  include more than one weight, each of the embedded weights can comprise the same or a different mass. 
     In many embodiments, the one or more embedded weights  383  can comprise a material having a specific gravity between 10.0-22.0. For example, in many embodiments, the one or more embedded weights  383  can comprise a material having a specific gravity greater than 10.0, greater than 11.0, greater than 12.0, greater than 13.0, greater than 14.0, greater than 15.0, greater than 16.0, greater than 17.0, greater than 18.0, or greater than 19.0. In embodiments where the one or more embedded weights  383  include more than one weight, each of the embedded weights can comprise the same or a different material. 
     v. Steep Crown Angle 
     Referring to  FIGS. 4-6 , in some embodiments, the golf club head  300  can further include a steep crown angle  388  to achieve the low and back head CG position. The steep crown angle  388  positions the back end of the crown  316  toward the sole  318  or ground, thereby lowering the club head CG position. 
     The crown angle  388  is measured as the acute angle between a crown axis  1090  and the front plane  1020 . In these embodiments, the crown axis  1090  is located in a cross-section of the club head taken along a plane positioned perpendicular to the ground plane  1030  and the front plane  1020 . The crown axis  1090  can be further described with reference to a top transition boundary and a rear transition boundary. 
     The club head  300  includes a top transition boundary extending between the front end  308  and the crown  316  from near the heel  320  to near the toe  322 . The top transition boundary includes a crown transition profile  390  when viewed from a side cross sectional view taken along a plane perpendicular to the front plane  1020  and perpendicular to the ground plane  1030  when the club head  300  is at an address position. The side cross sectional view can be taken along any point of the club head  300  from near the heel  320  to near the toe  322 . The crown transition profile  390  defines a front radius of curvature  392  extending from the front end  308  of the club head  300  where the contour departs from the roll radius and/or the bulge radius of the strikeface  304  to a crown transition point  394  indicating a change in curvature from the front radius of curvature  392  to the curvature of the crown  316 . In some embodiments, the front radius of curvature  392  comprises a single radius of curvature extending from the top end  393  of the strikeface perimeter  342  near the crown  316  where the contour departs from the roll radius and/or the bulge radius of the strikeface  304  to a crown transition point  394  indicating a change in curvature from the front radius of curvature  392  to one or more different curvatures of the crown  316 . 
     The club head  300  further includes a rear transition boundary extending between the crown  316  and the skirt  328  from near the heel  320  to near the toe  322 . The rear transition boundary includes a rear transition profile  396  when viewed from a side cross sectional view taken along a plane perpendicular to the front plane  1020  and perpendicular to the ground plane  1030  when the club head  300  is at an address position. The cross sectional view can be taken along any point of the club head  300  from near the heel  320  to near the toe  322 . The rear transition profile  396  defines a rear radius of curvature  398  extending from the crown  316  to the skirt  328  of the club head  300 . In many embodiments, the rear radius of curvature  398  comprises a single radius of curvature that transitions the crown  316  to the skirt  328  of the club head  300  along the rear transition boundary. A first rear transition point  402  is located at the junction between the crown  316  and the rear transition boundary. A second rear transition point  403  is located at the junction between the rear transition boundary and the skirt  328  of the club head  300 . 
     The front radius of curvature  392  of the top transition boundary can remain constant, or can vary from near the heel  320  to near the toe  322  of the club head  300 . Similarly, the rear radius of curvature  398  of the rear transition boundary can remain constant, or can vary from near the heel  320  to near the toe  322  of the club head  300 . 
     The crown axis  1090  extends between the crown transition point  394  near the front end  308  of the club head  300  and the rear transition point  402  near the back end  310  of the club head  300 . The crown angle  388  can remain constant, or can vary from near the heel  320  to near the toe  322  of the club head  300 . For example, the crown angle  388  can vary when the side cross sectional view is taken at different locations relative to the heel  320  and the toe  322 . 
     In the illustrated embodiment, the crown angle  388  near the toe  322  is approximately 72.25 degrees, the crown angle  388  near the heel  320  is approximately 64.5 degrees, and the crown angle  388  near the center of the golf club head is approximately 64.2 degrees. In many embodiments, the maximum crown angle  388  taken at any location from near the toe  322  to near the heel  320  is less than 79 degrees, less than approximately 78 degrees, less than approximately 77 degrees, less than approximately 76 degrees, less than approximately 75 degrees, less than approximately 74 degrees, less than approximately 73 degrees, less than approximately 72 degrees, less than approximately 71 degrees, less than approximately 70 degrees, less than approximately 69 degrees, or less than approximately 68 degrees. For example, in some embodiments, the maximum crown angle is between 50 degrees and 79 degrees, between 60 degrees and 79 degrees, or between 70 degrees and 79 degrees. 
     In other embodiments, the crown  388  angle near the toe  322  of the club head  300  can be less than approximately 79 degrees, less than approximately 78 degrees, less than approximately 77 degrees, less than approximately 76 degrees, less than approximately 75 degrees, less than approximately 74 degrees, less than approximately 73 degrees, less than approximately 72 degrees, less than approximately 71 degrees, less than approximately 70 degrees, less than approximately 69 degrees, or less than approximately 68 degrees. For example, the crown angle  388  taken along a side cross sectional view positioned approximately 1.0 inch toward the toe  322  from the geometric center  340  of the strikeface  304  can be less than 79 degrees, less than 78 degrees, less than 77 degrees, less than 76 degrees, less than 75 degrees, less than 74 degrees, less than 73 degrees, less than 72 degrees, less than 71 degrees, less than 70 degrees, less than 69 degrees, or less than 68 degrees. 
     Further, in other embodiments, the crown angle  388  near the heel  320  can be less than approximately 70 degrees, less than approximately 69 degrees, less than approximately 68 degrees, less than approximately 67 degrees, less than approximately 66 degrees, less than approximately 65 degrees, less than approximately 64 degrees, less than approximately 63 degrees, less than approximately 62 degrees, less than approximately 61 degrees, less than approximately 60 degrees, less than approximately 59 degrees. For example, the crown angle  388  taken along a side cross sectional view positioned approximately 1.0 inch toward the heel  320  from the geometric center  340  of the strikeface  304  can be less than approximately 70 degrees, less than approximately 69 degrees, less than approximately 68 degrees, less than approximately 67 degrees, less than approximately 66 degrees, less than approximately 65 degrees, less than approximately 64 degrees, less than approximately 63 degrees, less than approximately 62 degrees, less than approximately 61 degrees, less than approximately 60 degrees, less than approximately 59 degrees. 
     Further still, in other embodiments, the crown angle  388  near the center of the club head  300  can be less than 75 degrees, less than 74 degrees, less than 73 degrees, less than 72 degrees, less than 71 degrees, less than approximately 70 degrees, less than approximately 69 degrees, less than approximately 68 degrees, less than approximately 67 degrees, less than approximately 66 degrees, less than approximately 65 degrees, less than approximately 64 degrees, less than approximately 63 degrees, less than approximately 62 degrees, less than approximately 61 degrees, less than approximately 60 degrees, less than approximately 59 degrees. For example, the crown angle  388  taken along a side cross sectional view positioned approximately at the geometric center  340  of the strikeface  304  can be less than approximately 70 degrees, less than approximately 69 degrees, less than approximately 68 degrees, less than approximately 67 degrees, less than approximately 66 degrees, less than approximately 65 degrees, less than approximately 64 degrees, less than approximately 63 degrees, less than approximately 62 degrees, less than approximately 61 degrees, less than approximately 60 degrees, less than approximately 59 degrees. 
     In many embodiments, reducing the crown angle  388  compared to current club heads generates a steeper crown or a crown positioned closer to the ground plane  1030  when the club head  300  is at an address position. Accordingly, the reduced crown angle  388  can result in a lower head CG position compared to a club head with a higher crown angle. 
     vi. Hosel Sleeve Weight 
     In some embodiments, the head CG height  174  and/or head CG depth  172  can be achieved by reducing the mass of the hosel sleeve  334 . Removing excess weight from the hosel sleeve  334  results in increased discretionary weight that can be strategically repositioned to regions of the club head  300  to achieve the desired low and back club head CG position. 
     Reducing the mass of the hosel sleeve  334  can be achieved by thinning the sleeve walls, reducing the height of the hosel sleeve  334 , reducing the diameter of the hosel sleeve  334 , and/or by introducing voids in the walls of the hosel sleeve  334 . In many embodiments, the mass of the hosel sleeve  334  can be less than 6 grams, less than 5.5 grams, less than 5.0 grams, less than 4.5 grams, or less than 4.0 grams. In many embodiments, the club head  300  having the reduced mass hosel sleeve can result in a lower (close to the sole) and farther back (closer to the back end) club head CG position than a similar club head with a heavier hosel sleeve. 
     B. Aerodynamic Drag 
     In many embodiments, the club head  300  comprises a low and back club head CG position and an increased club head moment of inertia, in combination with reduced aerodynamic drag. 
     In many embodiments, the club head  300  experiences an aerodynamic drag force less than approximately 1.5 lbf, less than 1.4 lbf, less than 1.3 lbf, or less than 1.2 lbf when tested in a wind tunnel with a squared face and an air speed of 102 miles per hour (mph). In these or other embodiments, the club head  300  experiences an aerodynamic drag force less than approximately 1.5 lbf, less than 1.4 lbf, less than 1.3 lbf, or less than 1.2 lbf when simulated using computational fluid dynamics with a squared face and an air speed of 102 miles per hour (mph). In these embodiments, the airflow experienced by the club head  300  having the squared face is directed at the strikeface  304  in a direction perpendicular to the X′Y′ plane. The club head  300  having reduced aerodynamic drag can be achieved using various means, as described below. 
     i. Crown Angle Height 
     In some embodiments, reducing the crown angle  388  to form a steeper crown and lower head CG position may result in an undesired increase in aerodynamic drag due to increased air flow separation over the crown during a swing. To prevent increased drag associated with a reduced crown angle  388 , a maximum crown height  404  can be increased. Referring to  FIG. 4 , the maximum crown height  404  is the greatest distance between the surface of the crown  316  and the crown axis  1090  taken at any side cross sectional view of the club head  300  along a plane positioned parallel to the Y′Z′ plane. In many embodiments, a greater maximum crown height  404  results in the crown  316  having a greater curvature. A greater curvature in the crown  316  moves the location of the air flow separation during a swing further back on the club head  300 . In other words, a greater curvature allows the airflow to stay attached to club head  300  for a longer distance along the crown  316  during a swing. Moving the airflow separation point back on the crown  316  can result in reduced aerodynamic drag and increased club head swing speeds, thereby resulting in increased ball speed and distance. 
     In many embodiments, the maximum crown height  404  can be greater than approximately 0.20 inch (5 mm), greater than approximately 0.30 inch (7.5 mm), greater than approximately 0.40 inch (10 mm), greater than approximately 0.50 inch (12.5 mm), greater than approximately 0.60 inch (15 mm), greater than approximately 0.70 inch (17.5 mm), greater than approximately 0.80 inch (20 mm), greater than approximately 0.90 inch (22.5 mm), or greater than approximately 1.0 inch (25 mm). Further, in other embodiments, the maximum crown height can be within the range of 0.20 inch (5 mm) to 0.60 inch (15 mm), or 0.40 inch (10 mm) to 0.80 inch (20 mm), or 0.60 inch (15 mm) to 1.0 inch (25 mm). For example, in some embodiments, the maximum crown height  404  can be approximately 0.52 inch (13.3 mm), approximately 0.54 inch (13.8 mm), approximately 0.59 inch (15 mm), approximately 0.65 inch (16.5 mm), or approximately 0.79 inch (20 mm). 
     ii. Transition Profiles 
     In many embodiments, the transition profiles of the club head  300  from the strikeface  304  to the crown  316 , the strikeface  304  to the sole  318 , and/or the crown  316  to the sole  318  along the back end  310  of the club head  300  can affect the aerodynamic drag on the club head  300  during a swing. 
     In some embodiments, the club head  300  having the top transition boundary defining the crown transition profile  390 , and the rear transition boundary defining the rear transition profile  396  further includes a sole transition boundary defining a sole transition profile  410 . The sole transition boundary extends between the front end  308  and the sole  318  from near the heel  320  to near the toe  322 . The sole transition boundary includes a sole transition profile  410  when viewed from a side cross sectional view taken along a plane parallel to the Y′Z′ plane. The side cross sectional view can be taken along any point of the club head  300  from near the heel  320  to near the toe  322 . The sole transition profile  410  defines a sole radius of curvature  412  extending from the front end  308  of the club head  300  where the contour departs from the roll radius and/or the bulge radius of the strikeface  304  to a sole transition point  414  indicating a change in curvature from sole radius of curvature  412  to the curvature of the sole  318 . In some embodiments, the sole radius of curvature  412  comprises a single radius of curvature extending from the bottom end  413  of the strikeface perimeter  342  near the sole  318  where the contour departs from the roll radius and/or the bulge radius of the strikeface  304  to a sole transition point  414  indicating a change in curvature from the sole radius of curvature  412  to a curvature of the sole  414 . 
     In many embodiments, the crown transition profile  390 , the sole transition profile  410 , and the rear transition profile  396  can be similar to the crown transition, sole transition, and rear transition profiles described in U.S. patent Ser. No. 15/233,486, entitled “Golf Club Head with Transition Profiles to Reduce Aerodynamic Drag.” Further, the front radius of curvature  392  can be similar to the first crown radius of curvature, the sole radius of curvature  412  can be similar to the first sole radius of curvature, and the rear radius of curvature  398  can be similar to the rear radius of curvature described U.S. patent Ser. No. 15/233,486, entitled “Golf Club Head with Transition Profiles to Reduce Aerodynamic Drag.” 
     In some embodiments, front radius of curvature  392  can range from approximately 0.18 to 0.30 inches (0.46 to 0.76 cm). Further, in other embodiments, the front radius of curvature  392  can be less than 0.40 inches (1.02 cm), less than 0.375 inches (0.95 cm), less than 0.35 inches (0.89 cm), less than 0.325 inches (0.83 cm), or less than 0.30 inches 0.76 cm). For example, the front radius of curvature  392  may be approximately 0.18 inches (0.46 cm), 0.20 inches (0.51 cm), 0.22 inches (0.66 cm), 0.24 inches (0.61 cm), 0.26 inches (0.66 cm), 0.28 inches (0.71 cm), or 0.30 inches (0.76 cm). 
     In some embodiments, the sole radius of curvature  412  can range from approximately 0.25 to 0.50 inches (0.76 to 1.27 cm). For example, the sole radius of curvature  412  can be less than approximately 0.5 inches (1.27 cm), less than approximately 0.475 inches (1.21 cm), less than approximately 0.45 inches (1.14 cm), less than approximately 0.425 inches (1.08 cm), or less than approximately 0.40 inches (1.02 cm). For further example, the sole radius of curvature  412  can be approximately 0.30 inches (0.76 cm), 0.35 inches (0.89 cm), 0.40 inches (1.02 cm), 0.45 inches (1.14 cm), or 0.50 inches (1.27 cm). 
     In some embodiments, the rear radius of curvature  398  can range from approximately 0.10 to 0.25 inches (0.25 to 0.64 cm). For example, the rear radius of curvature  398  can be less than approximately 0.3 inches (0.76 cm), less than approximately 0.275 inches (0.70 cm), less than approximately 0.25 inches (0.64 cm), less than approximately 0.225 inches (0.57 cm), or less than approximately 0.20 inches (0.51 cm). For further example, the rear radius of curvature  398  can be approximately 0.10 inches (0.25 cm), 0.15 inches (0.38 cm), 0.20 inches (0.51 cm), or 0.25 inches (0.64 cm). 
     iii. Turbulators 
     Referring to  FIG. 7 , in some embodiments, the club head  300  can further include a plurality of turbulators  414 , as described in U.S. patent application Ser. No. 13/536,753, now U.S. Pat. No. 8,608,587, granted on Dec. 17, 2013, entitled “Golf Club Heads with Turbulators and Methods to Manufacture Golf Club Heads with Turbulators,” Which is incorporated fully herein by reference. In many embodiments, the plurality of turbulators  414  disrupt the airflow thereby creating small vortices or turbulence inside the boundary layer to energize the boundary layer and delay separation of the airflow on the crown  316  during a swing. 
     In some embodiments, the plurality of turbulators  414  can be adjacent to the crown transition point  594  of the club head  300 . The plurality of turbulators  414  project from an outer surface of the crown  316  and include a length extending between the front end  308  and the back end  310  of the club head  300 , and a width extending from the heel  320  to the toe  322  of the club head  300 . In many embodiments, the length of the plurality of turbulators  414  is greater than the width. In some embodiments, the plurality of turbulators  414  can comprise the same width. In some embodiments, the plurality of turbulators  414  can vary in height profile. In some embodiments, the plurality of turbulators  414  can be higher toward the apex of the crown  316  than in comparison to the front of the crown  316 . In other embodiments, the plurality of turbulators  414  can be higher toward the front of the crown  316 , and lower in height toward the apex of the crown  316 . In other embodiments, the plurality of turbulators  414  can comprise a constant height profile. Further, in many embodiments, at least a portion of at least one turbulator is located between the strikeface  304  and an apex of the crown  316 , and the spacing between adjacent turbulators is greater than the width of each of the adjacent turbulators. 
     iv. Back Cavity 
     Referring to  FIGS. 8-9 , in some embodiments, the club head  300  can further include a cavity  420  located at the back end  310  and in the trailing edge  328  of the club head  300 , similar to the cavity described in U.S. patent application Ser. No. 14/882,092, now U.S. Pat. No. 9,492,721 granted on Nov. 15, 2016, entitled “Golf Club Heads with Aerodynamic Features and Related Methods,” Which is incorporated fully herein by reference. In many embodiments, the cavity  420  can break the vortices generated behind golf club head  300  into smaller vortices to reduce the size of the wake and/or reduce drag. In some embodiments, breaking the vortices into smaller vortices can generate a region of high pressure behind golf club head  300 . In some embodiments, this region of high pressure can push golf club head  300  forward, reduce drag, and/or enhance the aerodynamic design of golf club head  300 . In many embodiments, the net effect of smaller vortices and reduced drag is an increase in the speed of golf club head  300 . This effect can lead to higher speeds at which a golf ball leaves strikeface  304  after impact to increase ball travel distance. 
     In many embodiments, the cavity  420  includes a back wall  422  that is oriented in a direction perpendicular to the X′Z′ plane and includes a width measured in a direction from the heel  320  to the toe  322 , a depth  424 , and a height  426 . The width of the cavity  420  can be approximately 1.0 inches (approximately 2.54 centimeters (cm)) to approximately 8 inch (approximately 20.32 cm), approximately 1.0 inches (approximately 2.54 cm) to approximately 2.25 inches (approximately 5.72 cm), or approximately 1.75 inches (approximately 4.5 cm) to approximately 2.25 inches (approximately 5.72 cm). For example, the width of the cavity  420  can be approximately 2.0 inches (5.08 cm), 3.0 inches (7.62 cm), 4.0 inches (10.16 cm), 5.0 inches (12.7 cm), 6.0 inches (15.24 cm), or 7.0 inches (17.78 cm). In some embodiments, the width of the cavity  420  can remain constant from near the top of the cavity  420  (toward the crown  316  of the club head  300 ) to near the bottom of the cavity  420  (toward the sole  318  of the club head  300 ). In other embodiments, the width of the cavity  420  can vary from near the top to near the bottom. In the illustrated embodiment of  FIG. 8 , the width of the cavity  420  is largest near the top and smallest near the bottom. In other embodiments, the width of the cavity  420  can vary according to any profile. For example, in other embodiments, the width of the cavity  420  can be longest at the top, at the bottom, at the center, or at any other location extending from the top to the bottom of the cavity  420 . 
     The depth  424  of the cavity  420  can be approximately 0.025 inch (approximately 0.127 cm) to approximately 0.250 inch (approximately 0.635 cm), or approximately 0.025 inch (approximately 0.127 cm) to approximately 0.150 inch (approximately 0.381 cm). For example, the depth  424  of the cavity  420  can be approximately 0.1 inch (approximately 0.254 cm), or approximately 0.05 inch (approximately 0.127 cm). In some embodiments, the depth  424  of the cavity  420  can remain constant between the heel and the toe and/or between the top and the bottom of the cavity  420 . In other embodiments, the depth  424  of the cavity  420  can vary between the heel and the toe and/or between the top and the bottom of the cavity  420 . For example, the depth  424  of the cavity  420  can be the largest near the heel, near the toe, near the crown, near the sole, near the center, or at any combination of the described locations. 
     The height  426  of the cavity  420  can be measured in a direction from the crown  316  to the sole  318 . The height  426  of the cavity  420  can be approximately 0.19 inch (approximately 0.48 cm) to approximately 0.21 inch (approximately 0.53 cm). In some embodiments, the height  426  of the cavity  420  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.50 inch (approximately 1.27 cm). In some embodiments, the height  426  of the cavity  420  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.40 inch (approximately 1.02 cm). In some embodiments, the height  426  of the cavity  420  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.30 inch (approximately 0.76 cm). In some embodiments, the height  426  of the cavity  420  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.20 inch (approximately 0.51 cm). In some embodiments, the height  426  of the cavity  420  can remain constant between the heel and the toe of the cavity  420 . In other embodiments, the height  426  of the cavity  420  can vary between the heel and the toe of the cavity  420 . For example, the height  426  of the cavity  420  can be the largest near the heel, near the toe, near the center, or at any combination of the described locations. 
     v. Hosel Structure 
     In some embodiments, the hosel structure  330  can have a smaller outer diameter to reduce the aerodynamic drag on the club head  300  during a swing, compared to a similar club head having a larger diameter hosel structure. In many embodiments, the hosel structure  330  has an outer diameter less than 0.545 inches. For example, the hosel structure  330  can have an outer diameter less than 0.60 inches, less than 0.59 inches, less than 0.58 inches, less than 0.57 inches, less than 0.56 inches, less than 0.55 inches, less than 0.54 inches, less than 0.53 inches, less than 0.52, less than 0.51 inches, or less than 0.50 inches. In many embodiments, the outer diameter of the hosel structure  330  is reduced while maintaining adjustability of the loft angle and/or lie angle of the club head  300 . 
     vi. Projected Area 
     In many embodiments, the club head  300  further comprises a front projected area and a side projected area. The front projected area is the area of the club head  300  visible from the front view, as illustrated in  FIG. 1 , and projected on the X′Y′ plane. The side projected area is the area of the club head  300  visible from the side view and projected on the Y′Z′ plane. 
     In many embodiments, the front projected area of the club head  300  can be between 0.00400 m 2  and 0.00700 m 2 . For example, in the illustrated embodiment, the front projected area of the club head is 0.00655 m 2 . In other embodiments, the front projected area can be between 0.00400 m 2  and 0.00665 m 2 , between 0.00400 m 2  and 0.00675 m 2 , between 0.00400 m 2  and 0.00685 m 2 , or between 0.00400 m 2  and 0.00695 m 2 . 
     In many embodiments, the side projected area of the club head  300  can be between 0.00500 m 2  and 0.00650 m 2 . For example, in the illustrated embodiment, the front projected area of the club head is 0.00579 m 2 . In other embodiments, the front projected area can be between 0.00545 m 2  and 0.00565 m 2 , between 0.00535 m 2  and 0.00575 m 2 , between 0.00525 m 2  and 0.00585 m 2 , or between 0.00515 m 2  and 0.00595 m 2 . 
     C. Balance of CG Position, Moment of Inertia, and Aerodynamic Drag 
     In current golf club head design, increasing or maximizing the moment of inertia of the club head and/or the head CG position can adversely affect other performance characteristics of the club head, such as aerodynamic drag. The club head  300  described herein increases or maximizes the club head moment of inertia, while simultaneously maintaining or reducing aerodynamic drag, as described in further detail below. Accordingly, the club head  300  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     II. Low Volume Driver-Type Club Head 
     According to another embodiment, a golf club head  500  can comprise a low volume and a low loft angle. In many embodiments, the golf club head  500  comprises a driver-type club head. In other embodiments, the golf club head  500  can comprise any type of golf club head having a loft angle and volume as described herein. In many embodiments, club head  500  comprises the same or similar parameters as club head  100 , wherein the parameters are described with the club head  100  reference numbers plus  400 . 
     In many embodiments, the loft angle of the club head  500  is less than approximately 16 degrees, less than approximately 15 degrees, less than approximately 14 degrees, less than approximately 13 degrees, less than approximately 12 degrees, less than approximately 11 degrees, or less than approximately 10 degrees. Further, in many embodiments, the volume of the club head  500  is less than approximately 450 cc, less than approximately 440 cc, less than approximately 430 cc, less than approximately 425 cc, less than approximately 400 cc, less than approximately 375 cc, or less than approximately 350 cc. In some embodiments, the volume of the club head can be approximately 300 cc-450 cc, approximately 300 cc-400 cc, approximately 325 cc-425 cc, approximately 350 cc-450 cc, approximately 400 cc-450 cc, approximately 420 cc-450 cc, or approximately 440 cc-450 cc. 
     In many embodiments, the length  562  of the club head  500  is greater than 4.85 inches. In other embodiments, the length  562  of the club head  500  is greater than 4.5 inches, greater than 4.6 inches, greater than 4.7 inches, greater than 4.8, greater than 4.9 inches, or greater than 5.0 inches. For example, in some embodiments, the length  562  of the club head  500  can be between 4.6-5.0 inches, between 4.7-5.0 inches, between 4.8-5.0 inches, between 4.85-5.0 inches, or between 4.9-5.0 inches. 
     In many embodiments, the depth  560  of the club head  500  is at least 0.70 inches less than the length  562  of the club head  500 . In many embodiments, the depth  560  of the club head  500  is greater than 4.75 inches. In other embodiments, the depth  360  of the club head  500  is greater than 4.5 inches, greater than 4.6 inches, greater than 4.7 inches, greater than 4.8, greater than 4.9 inches, or greater than 5.0 inches. For example, in some embodiments, the depth  560  of the club head  500  can be between 4.6-5.0 inches, between 4.7-5.0 inches, between 4.75-5.0 inches, between 4.8-5.0 inches, or between 4.9-5.0 inches. 
     In many embodiments, the height  564  of the club head is less than approximately 2.8 inches. In other embodiments, the height  564  of the club head  500  is less than 3.0 inches, less than 2.9 inches, less than 2.8 inches, less than 2.7, or less than 2.6 inches. For example, in some embodiments, the height  564  of the club head  500  can be between 2.0-2.8 inches, between 2.2-2.8 inches, between 2.5-2.8 inches, or between 2.5-3.0 inches. Further, in many embodiments, the face height  544  of the club head  500  can be approximately 1.3 inches (33 mm) to approximately 2.8 inches (71 mm). Further still, in many embodiments, the club head  500  can comprise a mass between 185 grams and 225 grams. 
     The club head  500  further comprises a balance of various additional parameters, such as head CG position, club head moment of inertia, and aerodynamic drag, to provide both improved impact performance characteristics (e.g. spin, launch angle, speed, forgiveness) and swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact). In many embodiments, the balance of parameters described below provides improved impact performance while maintaining or improving swing performance characteristics. Further, in many embodiments, the balance of parameters described below provides improved swing performance characteristics while maintaining or improving impact performance characteristics. 
     A. Center of Gravity Position and Moment of Inertia 
     In many embodiments, a low and back club head CG and increased moment of inertia can be achieved by increasing discretionary weight and repositioning discretionary weight in regions of the club head having maximized distances from the head CG. Increasing discretionary weight can be achieved by thinning the crown and/or using optimized materials, as described above relative to the head CG position. Repositioning discretionary weight to maximize the distance from the head CG can be achieved using removable weights, embedded weights, or a steep crown angle, as described above relative to the head CG position. 
     In many embodiments, the club head  500  comprises a crown-to-sole moment of inertia I xx  greater than approximately 3000 g·cm 2 , greater than approximately 3250 g·cm 2 , greater than approximately 3500 g·cm 2 , greater than approximately 3750 g·cm 2 , greater than approximately 4000 g·cm 2 , greater than approximately 4250 g·cm 2 , greater than approximately 4500 g·cm 2 , greater than approximately 4750 g·cm 2 , greater than approximately 5000 g·cm 2 , greater than approximately 5250 g·cm 2 , greater than approximately 5500 g·cm 2 , greater than approximately 5750 g·cm 2 , greater than approximately 6000 g·cm 2 , greater than approximately 6250 g·cm 2 , greater than approximately 6500 g·cm 2 , greater than approximately 6750 g·cm 2 , or greater than approximately 7000 g·cm 2 . 
     In many embodiments, the club head  500  comprises a heel-to-toe moment of inertia I yy  greater than approximately 5000 g·cm 2 , greater than approximately 5250 g·cm 2 , greater than approximately 5500 g·cm 2 , greater than approximately 5750 g·cm 2 , greater than approximately 6000 g·cm 2 , greater than approximately 6250 g·cm 2 , greater than approximately 6500 g·cm 2 , greater than approximately 6750 g·cm 2 , or greater than approximately 7000 g·cm 2 . 
     In many embodiments, the club head  500  comprises a combined moment of inertia (i.e. the sum of the crown-to-sole moment of inertia I xx  and the heel-to-toe moment of inertia I yy ) greater than 8000 g·cm 2 , greater than 8500 g·cm 2 , greater than 8750 g·cm 2 , greater than 9000 g·cm 2 , greater than 9250 g·cm 2 , greater than 9500 g·cm 2 , greater than 9750 g·cm 2 , greater than 10000 g·cm 2 , greater than 10250 g·cm 2 , greater than 10500 g·cm 2 , greater than 10750 g·cm 2 , greater than 11000 g·cm 2 , greater than 11250 g·cm 2 , greater than 11500 g·cm 2 , greater than 11750 g·cm 2 , or greater than 12000 g·cm 2 . 
     In many embodiments, the club head  500  comprises a head CG height  574  less than approximately 0.20 inches, less than approximately 0.15 inches, less than approximately 0.10 inches, less than approximately 0.09 inches, less than approximately 0.08 inches, less than approximately 0.07 inches, less than approximately 0.06 inches, or less than approximately 0.05 inches. Further, in many embodiments, the club head  500  comprises a head CG height  574  having an absolute value less than approximately 0.20 inches, less than approximately 0.15 inches, less than approximately 0.10 inches, less than approximately 0.09 inches, less than approximately 0.08 inches, less than approximately 0.07 inches, less than approximately 0.06 inches, or less than approximately 0.05 inches. 
     In many embodiments, the club head  500  comprises a head CG depth  572  greater than approximately 1.2 inches, greater than approximately 1.3 inches, greater than approximately 1.4 inches, greater than approximately 1.5 inches, greater than approximately 1.6 inches, greater than approximately 1.7 inches, greater than approximately 1.8 inches, greater than approximately 1.9 inches, or greater than approximately 2.0 inches. 
     In some embodiments, the club head  500  can comprise a first performance characteristic less than or equal to 0.56, wherein the first performance characteristic is defined as a ratio between (a) the difference between 72 mm and the face height  544 , and (b) the head CG depth  572 . In these or other embodiments, the club head  500  can comprise a second performance characteristic greater than or equal to 425 cc, wherein the second performance characteristic is defined as the sum of (a) the volume of the club head  500 , and (b) a ratio between the head CG depth  572  and the absolute value of the head CG height  574 . In some embodiments, the second performance characteristic can be greater than or equal to 450 cc, greater than or equal to 475 cc, greater than or equal to 490 cc, greater than or equal to 495 cc, greater than or equal to 500 cc, greater than or equal to 505 cc, or greater than or equal to 510 cc. 
     The club head  500  having the reduced head CG height  574  can reduce the backspin of a golf ball on impact compared to a similar club head having a higher head CG height. In many embodiments, reduced backspin can increase both ball speed and travel distance for improve club head performance. Further, the club head  500  having the increased head CG depth  572  can increase the heel-to-toe moment of inertia compared to a similar club head having a head CG depth closer to the strikeface. Increasing the heel-to-toe moment of inertia can increase club head forgiveness on impact to improve club head performance. Further still, the club head  500  having the increased head CG depth  572  can increase launch angle of a golf ball on impact by increasing the dynamic loft of the club head at delivery, compared to a similar club head having a head CG depth closer to the strikeface. 
     The head CG height  574  and/or head CG depth  572  can be achieved by reducing weight of the club head  500  in various regions, thereby increasing discretionary weight, and repositioning discretionary weight in strategic regions of the club head to shift the head CG lower and farther back. Various means to reduce and reposition club head weight are described below. 
     i. Thin Regions 
     In some embodiments, the head CG height  574  and/or head CG depth  572  can be achieved by thinning various regions of the club head  500  to remove excess weight. Removing excess weight results in increased discretionary weight that can be strategically repositioned to regions of the club head  500  to achieve the desired low and back club head CG position. 
     In many embodiments, the club head  500  can have one or more thin regions. The thinned regions can be similar or identical to the one or more thin regions  376  of club head  300 . The one or more thin regions can be positioned on the strikeface  504 , the body  502 , or a combination of the strikeface  504  and the body  502 . Further, the one or more thin regions can be positioned on any region of the body  502 , including the crown  516 , the sole  518 , the heel  520 , the toe  522 , the front end  508 , the back end  510 , the skirt  528 , or any combination of the described positions. For example, in some embodiments, the one or more thin regions can be positioned on the crown  516 . For further example, the one or more thin regions can be positioned on a combination of the strikeface  504  and the crown  516 . For further example, the one or more thin regions can be positioned on a combination of the strikeface  504 , the crown  516 , and the sole  518 . For further example, the entire body  502  and/or the entire strikeface  504  can comprise a thin region. 
     In embodiments where one or more thin regions are positioned on the strikeface  504 , the thickness of the strikeface  504  can vary defining a maximum strikeface thickness and a minimum strikeface thickness. In these embodiments, the minimum strikeface thickness can be less than 0.10 inches, less than 0.09 inches, less than 0.08 inches, less than 0.07 inches, less than 0.06 inches, less than 0.05 inches, less than 0.04 inches, or less than 0.03 inches. In these or other embodiments, the maximum strikeface thickness can be less than 0.20 inches, less than 0.19 inches, less than 0.18 inches, less than 0.17 inches, less than 0.16 inches, less than 0.15 inches, less than 0.14 inches, less than 0.13 inches, less than 0.12 inches, less than 0.11 inches, or less than 0.10 inches. 
     In embodiments where one or more thin regions are positioned on the body  502 , the thin regions can comprise a thickness less than approximately 0.020 inches. In other embodiments, the thin regions comprise a thickness less than 0.025 inches, less than 0.020 inches, less than 0.019 inches, less than 0.018 inches, less than 0.017 inches, less than 0.016 inches, less than 0.015 inches, less than 0.014 inches, less than 0.013 inches, less than 0.012 inches, or less than 0.010 inches. For example, the thin regions can comprise a thickness between approximately 0.010-0.025 inches, between approximately 0.013-0.020 inches, between approximately 0.014-0.020 inches, between approximately 0.015-0.020 inches, between approximately 0.016-0.020 inches, between approximately 0.017-0.020 inches, or between approximately 0.018-0.020 inches. 
     In the illustrated embodiment, the thin regions vary in shape and position and cover approximately 25% of the surface area of club head  500 . In other embodiments, the thin regions can cover approximately 20-30%, approximately 15-35%, approximately 15-25%, approximately 10-25%, approximately 15-30%, or approximately 20-50% of the surface area of club head  500 . Further, in other embodiments, the thin regions can cover up to 5%, up to 10%, up to 15%, up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, or up to 50% of the surface area of club head  500 . 
     In many embodiments, the crown  518  can comprise one or more thin regions, such that approximately 51% of the surface area of the crown comprises thin regions. In other embodiments, the crown  516  can comprise one or more thin regions, such that up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, up to 50%, up to 55%, up to 60%, up to 65%, up to 70%, or up to 75% of the crown comprises thin regions. For example, in some embodiments, approximately 40-60% of the crown can comprise thin regions. For further example, in other embodiments, approximately 50-100%, approximately 40-80%, approximately 35-65%, approximately 30-70%, or approximately 25-75% of the crown  516  can comprise thin regions. In some embodiments, the crown  516  can comprise one or more thin regions, wherein each of the one or more thin regions become thinner in a gradient fashion. In this exemplary embodiment, the one or more thin regions of the crown  516  extend in a heel-to-toe direction, and each of the one or more thin regions decrease in thickness in a direction from the strikeface  504  toward the back end  510 . 
     In many embodiments, the sole  518  can comprise one or more thin regions, such that approximately 64% of the surface area of the sole comprises thin regions. In other embodiments, the sole  518  can comprise one or more thin regions, such that up to 20%, up to 25%, up to 300%, up to 35%, up to 40%, up to 45%, up to 50%, up to 55%, up to 60%, up to 65%, up to 70%, up to 75%, up to 80%, up to 85%, or up to 90% of the sole comprises thin regions. For example, in some embodiments, approximately 40-60% of the sole can comprise thin regions. For further example, in other embodiments, approximately 50-100%, approximately 40-80%, approximately 35-65%, approximately 30-70%, or approximately 25-75% of the sole  518  can comprise thin regions. 
     The thinned regions can comprise any shape, such as circular, triangular, square, rectangular, ovular, or any other polygon or shape with at least one curved surface. Further, one or more thinned regions can comprise the same shape as or a different shape than the remaining thinned regions. 
     In many embodiments, club head  500  having thin regions can be manufacturing using centrifugal casting. In these embodiments, centrifugal casting allows the club head  500  to have thinner walls than a club head manufactured using conventional casting. In other embodiments, portions of the club head  500  having thin regions can be manufactured using other suitable methods, such as stamping, forging, or machining. In embodiments where portions of the club head  500  having thin regions are manufactured using stamping, forging, or machining, the portions of the club head  500  can be coupled using epoxy, tape, welding, mechanical fasteners, or other suitable methods. 
     ii. Optimized Materials 
     In some embodiments, the strikeface  504  and/or the body  502  can comprise an optimized material having increased specific strength and/or increased specific flexibility. The specific flexibility is measured as a ratio of the yield strength to the elastic modulus of the optimized material. Increasing specific strength and/or specific flexibility can allow portions of the club head to be thinned, while maintaining durability. 
     In some embodiments, the first material of the strikeface  504  can be an optimized material, as described in U.S. Provisional Patent Appl. No. 62/399,929, entitled “Golf Club Heads with Optimized Material Properties.” In these or other embodiments, the first material comprising an optimized titanium alloy can have a specific strength greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 910,000 PSI/lb/in 3  (227 MPa/g/cm 3 ), greater than or equal to approximately 920,000 PSI/lb/in 3  (229 MPa/g/cm 3 ), greater than or equal to approximately 930,000 PSI/lb/in 3  (232 MPa/g/cm 3 ), greater than or equal to approximately 940,000 PSI/lb/in 3  (234 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 960,000 PSI/lb/in 3  (239 MPa/g/cm 3 ), greater than or equal to approximately 970,000 PSI/lb/in 3  (242 MPa/g/cm 3 ), greater than or equal to approximately 980,000 PSI/lb/in 3  (244 MPa/g/cm 3 ), greater than or equal to approximately 990,000 PSI/lb/in 3  (247 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), greater than or equal to approximately 1,100,000 PSI/lb/in 3  (274 MPa/g/cm 3 ), or greater than or equal to approximately 1,150,000 PSI/lb/in 3  (286 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the first material comprising an optimized titanium alloy can have a specific flexibility greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0091, greater than or equal to approximately 0.0092, greater than or equal to approximately 0.0093, greater than or equal to approximately 0.0094, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0096, greater than or equal to approximately 0.0097, greater than or equal to approximately 0.0098, greater than or equal to approximately 0.0099, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, or greater than or equal to approximately 0.0120. 
     In these or other embodiments, the first material comprising an optimized steel alloy can have a specific strength greater than or equal to approximately 650,000 PSI/lb/in 3  (162 MPa/g/cm 3 ), greater than or equal to approximately 700,000 PSI/lb/in 3  (174 MPa/g/cm 3 ), greater than or equal to approximately 750,000 PSI/lb/in 3  (187 MPa/g/cm 3 ), greater than or equal to approximately 800,000 PSI/lb/in 3  (199 MPa/g/cm 3 ), greater than or equal to approximately 810,000 PSI/lb/in 3  (202 MPa/g/cm 3 ), greater than or equal to approximately 820,000 PSI/lb/in 3  (204 MPa/g/cm 3 ), greater than or equal to approximately 830,000 PSI/lb/in 3  (207 MPa/g/cm 3 ), greater than or equal to approximately 840,000 PSI/lb/in 3  (209 MPa/g/cm 3 ), greater than or equal to approximately 850,000 PSI/lb/in 3  (212 MPa/g/cm 3 ), greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), greater than or equal to approximately 1,100,000 PSI/lb/in 3  (274 MPa/g/cm 3 ), greater than or equal to approximately 1,115,000 PSI/lb/in 3  (278 MPa/g/cm 3 ), or greater than or equal to approximately 1,120,000 PSI/lb/in 3  (279 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the first material comprising an optimized steel alloy can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0065, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, greater than or equal to approximately 0.0120, greater than or equal to approximately 0.0125, greater than or equal to approximately 0.0130, greater than or equal to approximately 0.0135, greater than or equal to approximately 0.0140, greater than or equal to approximately 0.0145, or greater than or equal to approximately 0.0150. 
     In these embodiments, the increased specific strength and/or increased specific flexibility of the optimized first material allow the strikeface  504 , or portions thereof, to be thinned, as described above, while maintaining durability. Thinning of the strikeface  504  can reduce the weight of the strikeface  504 , thereby increasing discretionary weight to be strategically positioned in other areas of the club head  500  to position the head CG low and back and/or increase the club head moment of inertia. 
     In some embodiments, the second material of the body  502  can be an optimized material, as described in U.S. Provisional Patent Appl. No. 62/399,929, entitled “Golf Club Heads with Optimized Material Properties.” In these or other embodiments, the second material comprising an optimized titanium alloy can have a specific strength greater than or equal to approximately 730,500 PSI/lb/in 3  (182 MPa/g/cm 3 ). For example, the specific strength of the optimized titanium alloy can be greater than or equal to approximately 650,000 PSI/lb/in 3  (162 MPa/g/cm 3 ), greater than or equal to approximately 700,000 PSI/lb/in 3  (174 MPa/g/cm 3 ), greater than or equal to approximately 750,000 PSI/lb/in 3  (187 MPa/g/cm 3 ), greater than or equal to approximately 800,000 PSI/lb/in 3  (199 MPa/g/cm 3 ), greater than or equal to approximately 850,000 PSI/lb/in 3  (212 MPa/g/cm 3 ), greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), or greater than or equal to approximately 1,100,000 PSI/lb/in 3  (272 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the second material comprising an optimized titanium alloy can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0065, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, or greater than or equal to approximately 0.0120. 
     In these or other embodiments, the second material comprising an optimized steel can have a specific strength greater than or equal to approximately 500,000 PSI/lb/in 3  (125 MPa/g/cm 3 ), greater than or equal to approximately 510,000 PSI/lb/in 3  (127 MPa/g/cm 3 ), greater than or equal to approximately 520,000 PSI/lb/in 3  (130 MPa/g/cm 3 ), greater than or equal to approximately 530,000 PSI/lb/in 3  (132 MPa/g/cm 3 ), greater than or equal to approximately 540,000 PSI/lb/in 3  (135 MPa/g/cm 3 ), greater than or equal to approximately 550,000 PSI/lb/in 3  (137 MPa/g/cm 3 ), greater than or equal to approximately 560,000 PSI/lb/in 3  (139 MPa/g/cm 3 ), greater than or equal to approximately 570,000 PSI/lb/in 3  (142 MPa/g/cm 3 ), greater than or equal to approximately 580,000 PSI/lb/in 3  (144 MPa/g/cm 3 ), greater than or equal to approximately 590,000 PSI/lb/in 3  (147 MPa/g/cm 3 ), greater than or equal to approximately 600,000 PSI/lb/in 3  (149 MPa/g/cm 3 ), greater than or equal to approximately 625,000 PSI/lb/in 3  (156 MPa/g/cm 3 ), greater than or equal to approximately 675,000 PSI/lb/in 3  (168 MPa/g/cm 3 ), greater than or equal to approximately 725,000 PSI/lb/in 3  (181 MPa/g/cm 3 ), greater than or equal to approximately 775,000 PSI/lb/in 3  (193 MPa/g/cm 3 ), greater than or equal to approximately 825,000 PSI/lb/in 3  (205 MPa/g/cm 3 ), greater than or equal to approximately 875,000 PSI/lb/in 3  (218 MPa/g/cm 3 ), greater than or equal to approximately 925,000 PSI/lb/in 3  (230 MPa/g/cm 3 ), greater than or equal to approximately 975,000 PSI/lb/in 3  (243 MPa/g/cm 3 ), greater than or equal to approximately 1,025,000 PSI/lb/in 3  (255 MPa/g/cm 3 ), greater than or equal to approximately 1,075,000 PSI/lb/in 3  (268 MPa/g/cm 3 ), or greater than or equal to approximately 1,125,000 PSI/lb/in 3  (280 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the second material comprising an optimized steel can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0062, greater than or equal to approximately 0.0064, greater than or equal to approximately 0.0066, greater than or equal to approximately 0.0068, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0072, greater than or equal to approximately 0.0076, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0084, greater than or equal to approximately 0.0088, greater than or equal to approximately 0.0092, greater than or equal to approximately 0.0096, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, greater than or equal to approximately 0.0120, greater than or equal to approximately 0.0125, greater than or equal to approximately 0.0130, greater than or equal to approximately 0.0135, greater than or equal to approximately 0.0140, greater than or equal to approximately 0.0145, or greater than or equal to approximately 0.0150. 
     In these embodiments, the increased specific strength and/or increased specific flexibility of the optimized second material allow the body  502 , or portions thereof, to be thinned, while maintaining durability. Thinning of the body  502  can reduce club head weight, thereby increasing discretionary weight to be strategically positioned in other areas of the club head  500  to position the head CG low and back and/or increase the club head moment of inertia. 
     iii. Removable Weights 
     In some embodiments, the club head  500  can include one or more weight structures  580  comprising one or more removable weights  582 . The one or more weight structures  580  and/or the one or more removable weights  582  can be located towards the sole  518  and towards the back end  510 , thereby positioning the discretionary weight on the sole  518  and near the back end  510  of the club head  500  to achieve a low and back head CG position. In many embodiments, the one or more weight structures  580  removably receive the one or more removable weights  582 . In these embodiments, the one or more removable weights  582  can be coupled to the one or more weight structures  580  using any suitable method, such as a threaded fastener, an adhesive, a magnet, a snap fit, or any other mechanism capable of securing the one or more removable weights to the one or more weight structures  580 . 
     The weight structure  580  and/or removable weight  582  can be located relative to a clock grid  2000  (illustrated in  FIG. 3 ), which can be aligned with respect to the strikeface  504  when viewed from a top view. The clock grid comprises at least a 12 o&#39;clock ray, a 3 o&#39;clock ray, a 4 o&#39;clock ray, a 5 o&#39;clock ray, a 6 o&#39;clock ray, a 7 o&#39;clock ray, a 8 o&#39;clock ray, and a 9 o&#39;clock ray. For example, the clock grid  2000  comprises a 12 o&#39;clock ray  2012 , which is aligned with the geometric center  540  of the strikeface  504 . The 12 o&#39;clock ray  2012  is orthogonal to the X′Y′ plane. Clock grid  2000  can be centered along 12 o&#39;clock ray  2012 , at a midpoint between the front end  508  and back end  510  of the club head  500 . In the same or other examples, clock grid centerpoint  2010  can be centered proximate to a geometric centerpoint of golf club head  500  when viewed from a bottom view. The clock grid  2000  also comprises a 3 o&#39;clock ray  2003  extending towards the heel  520 , and a 9 o&#39;clock ray  2009  extending towards the toe  522  of the club head  500 . 
     A weight perimeter  584  of the weight structure  580  is located in the present embodiment towards the back end  510 , at least partially bounded between a 4 o&#39;clock ray  2004  and 8 o&#39;clock ray  2008  of clock grid  2000 , while a weight center  586  of a removable weight  582  positioned within weight structure  580  is located between a 5 o&#39;clock ray  2005  and a 7 o&#39;clock ray  2007 . In examples such as the present one, the weight perimeter  584  is fully bounded between the 4 o&#39;clock ray  2004  and the 8 o&#39;clock ray  2008 . Although the weight perimeter  584  is defined external to the club head  500  in the present example, there can be other examples where the weight perimeter  584  may extend into an interior of, or be defined within, the club head  500 . In some examples, the location of the weight structure  580  can be established with respect to a broader area. For instance, in such examples, the weight perimeter  584  of the weight structure  580  can be located towards the back end  510 , at least partially bounded between the 4 o&#39;clock ray  2004  and 9 o&#39;clock ray  2009  of the clock grid  2000 , while the weight center  586  can be located between the 5 o&#39;clock ray  2005  and 8 o&#39;clock ray  2008 . 
     In the present example, the weight structure  580  protrudes from the external contour of the sole  518 , and is thus at least partially external to allow for greater adjustment of the head CG  570 . In some examples, the weight structure  580  can comprise a mass of approximately 2 grams to approximately 50 grams, and/or a volume of approximately 1 cc to approximately 30 cc. In other examples, the weight structure  580  can remain flush with the external contour of the body  502 . 
     In many embodiments, the removable weight  582  can comprise a mass of approximately 0.5 grams to approximately 30 grams, and can be replaced with one or more other similar removable weights to adjust the location of the head CG  570 . In the same or other examples, the weight center  586  can comprise at least one of a center of gravity of the removable weight  582 , and/or a geometric center of removable weight  582 . 
     iv. Embedded Weights 
     In some embodiments, the club head  500  can include one or more embedded weights to position the discretionary weight on the sole  518 , in the skirt  528 , and/or near the back end  510  of the club head  500  to achieve a low and back head CG position. The one or more embedded weights of club head  500  can be similar or identical to the one or more embedded weights  383  of club head  300 . In many embodiments, the one or more embedded weights are permanently fixed to or within the club head  500 . In these embodiments, the embedded weight can be similar to the high density metal piece (HDMP) described in U.S. Provisional Patent Appl. No. 62/372,870, entitled “Embedded High Density Casting.” 
     In many embodiments, the one or more embedded weights are positioned near the back end  510  of the club head  500 . For example, a weight center of the embedded weight can be located between the 5 o&#39;clock ray  2005  and 7 o&#39;clock ray  2007 , or between the 5 o&#39;clock ray  2005  and 8 o&#39;clock ray  2008  of the clock grid  2000 . In many embodiments, the one or more embedded weights can be positioned on the skirt and near the back end of the club head, on the sole and near the back end of the club head, or on the skirt and the sole near the back end of the club head. 
     In many embodiments, the weight center of the one or more embedded weights is positioned within 0.10 inches, within 0.20 inches, within 0.30 inches, within 0.40 inches, within 0.50 inches, within 0.60 inches, within 0.70 inches, within 0.80 inches, within 0.90 inches, within 1.0 inches, within 1.1 inches, within 1.2 inches, within 1.3 inches, within 1.4 inches, or within 1.5 inches of a perimeter of the club head  500  when viewed from a top view. In these embodiments, the proximity of the embedded weight to the perimeter of the club head  500  can maximize the low and back head CG position, the crown-to-sole moment of inertia I xx , and/or the heel-to-toe moment of inertia I yy . 
     In many embodiments, the weight center of the one or more embedded weights is positioned at a distance from the head CG  570  greater than 1.6 inches, greater than 1.7 inches, greater than 1.8 inches, greater than 1.9 inches, greater than 2.0 inches, greater than 2.1 inches, greater than 2.2 inches, greater than 2.3 inches, greater than 2.4 inches, greater than 2.5 inches, greater than 2.6 inches, greater than 2.7 inches, greater than 2.8 inches, greater than 2.9 inches, or greater than 3.0 inches. 
     In many embodiments, the weight center of the one or more embedded weights is positioned at a distance from the geometric center  540  of the strikeface  504  greater than 4.0 inches, greater than 4.1 inches, greater than 4.2 inches, greater than 4.3 inches, greater than 4.4 inches, greater than 4.5 inches, greater than 4.6 inches, greater than 4.7 inches, greater than 4.8 inches, greater than 4.9 inches, or greater than 5.0 inches. 
     In many embodiments, the one or more embedded weights can comprise a mass between 3.0-70 grams. For example, in some embodiments, the one or more embedded weights can comprise a mass between 3.0-25 grams, between 10-30 grams, between 20-40 grams, between 30-50 grams, between 40-60 grams, or between 50-70 grams. In embodiments where the one or more embedded weights include more than one weight, each of the embedded weights can comprise the same or a different mass. 
     In many embodiments, the one or more embedded weights can comprise a material having a specific gravity between 10.0-22.0. For example, in many embodiments, the one or more embedded weights can comprise a material having a specific gravity greater than 10.0, greater than 11.0, greater than 12.0, greater than 13.0, greater than 14.0, greater than 15.0, greater than 16.0, greater than 17.0, greater than 18.0, or greater than 19.0. In embodiments where the one or more embedded weights include more than one weight, each of the embedded weights can comprise the same or a different material. 
     v. Steep Crown Angle 
     In some embodiments, the golf club head  500  can further include a steep crown angle  588  to achieve the low and back head CG position. The steep crown angle  588  positions the back end of the crown  516  toward the sole or ground, thereby lowering the club head CG position. 
     The crown angle  588  is measured as the acute angle between a crown axis  1090  and the front plane  1020 . In these embodiments, the crown axis  1090  is located in a cross-section of the club head taken along a plane positioned perpendicular to the ground plane  1030  and the front plane  1020 . The crown axis  1090  can be further described with reference to a top transition boundary and a rear transition boundary. 
     The club head  500  includes a top transition boundary extending between the front end  508  and the crown  516  from near the heel  520  to near the toe  522 . The top transition boundary includes a crown transition profile  590  when viewed from a side cross sectional view taken along a plane perpendicular to the front plane  1020  and perpendicular to the ground plane  1030  when the club head  500  is at an address position. The side cross sectional view can be taken along any point of the club head  500  from near the heel  520  to near the toe  522 . The crown transition profile  590  defines a front radius of curvature  592  extending from the front end  508  of the club head  500  where the contour departs from the roll radius and/or the bulge radius of the strikeface  504  to a crown transition point  594  indicating a change in curvature from the front radius of curvature  592  to the curvature of the crown  516 . In some embodiments, the front radius of curvature  592  comprises a single radius of curvature extending from the top end  593  of the strikeface perimeter  542  near the crown  516  where the contour departs from the roll radius and/or the bulge radius of the strikeface  504  to a crown transition point  594  indicating a change in curvature from the front radius of curvature  592  to one or more different curvatures of the crown  516 . 
     The club head  500  further includes a rear transition boundary extending between the crown  516  and the skirt  528  from near the heel  520  to near the toe  522 . The rear transition boundary includes a rear transition profile  596  when viewed from a side cross sectional view taken along a plane perpendicular to the front plane  1020  and perpendicular to the ground plane  1030  when the club head  500  is at an address position. The cross sectional view can be taken along any point of the club head  500  from near the heel  520  to near the toe  522 . The rear transition profile  596  defines a rear radius of curvature  598  extending from the crown  516  to the skirt  528  of the club head  500 . In many embodiments, the rear radius of curvature  598  comprises a single radius of curvature that transitions the crown  516  to the skirt  528  of the club head  500  along the rear transition boundary. A first rear transition point  602  is located at the junction between the crown  516  and the rear transition boundary. A second rear transition point  603  is located at the junction between the rear transition boundary and the skirt  528  of the club head  500 . 
     The front radius of curvature  592  of the top transition boundary can remain constant, or can vary from near the heel  520  to near the toe  522  of the club head  500 . Similarly, the rear radius of curvature  598  of the rear transition boundary can remain constant, or can vary from near the heel  520  to near the toe  522  of the club head  500 . 
     The crown axis  1090  extends between the crown transition point  594  near the front end  508  of the club head  500  and the rear transition point  602  near the back end  510  of the club head  500 . The crown angle  388  can remain constant, or can vary from near the heel  520  to near the toe  522  of the club head  500 . For example, the crown angle  588  can vary when the side cross sectional view is taken at different locations relative to the heel  520  and the toe  522 . 
     In the illustrated embodiment, the crown angle  588  near the toe  522  is approximately 72.25 degrees, the crown angle  588  near the heel  520  is approximately 64.5 degrees, and the crown angle  588  near the center of the golf club head  500  is approximately 64.2 degrees. In many embodiments, the maximum crown angle  588  taken at any location from near the toe  522  to near the heel  520  is less than 79 degrees, less than approximately 78 degrees, less than approximately 77 degrees, less than approximately 76 degrees, less than approximately 75 degrees, less than approximately 74 degrees, less than approximately 73 degrees, less than approximately 72 degrees, less than approximately 71 degrees, less than approximately 70 degrees, less than approximately 69 degrees, or less than approximately 68 degrees. For example, in some embodiments, the maximum crown angle is between 50 degrees and 79 degrees, between 60 degrees and 79 degrees, or between 70 degrees and 79 degrees. 
     In other embodiments, the crown angle  588  near the toe  522  of the club head  500  can be less than approximately 79 degrees, less than approximately 78 degrees, less than approximately 77 degrees, less than approximately 76 degrees, less than approximately 75 degrees, less than approximately 74 degrees, less than approximately 73 degrees, less than approximately 72 degrees, less than approximately 71 degrees, less than approximately 70 degrees, less than approximately 69 degrees, or less than approximately 68 degrees. For example, the crown angle  588  taken along a side cross sectional view positioned approximately 1.0 inch toward the toe  522  from the geometric center  540  of the strikeface  504  can be less than 79 degrees, less than 78 degrees, less than 77 degrees, less than 76 degrees, less than 75 degrees, less than 74 degrees, less than 73 degrees, less than 72 degrees, less than 71 degrees, less than 70 degrees, less than 69 degrees, or less than 68 degrees. 
     Further, in other embodiments, the crown angle  588  near the heel  522  can be less than approximately 70 degrees, less than approximately 69 degrees, less than approximately 68 degrees, less than approximately 67 degrees, less than approximately 66 degrees, less than approximately 65 degrees, less than approximately 64 degrees, less than approximately 63 degrees, less than approximately 62 degrees, less than approximately 61 degrees, less than approximately 60 degrees, less than approximately 59 degrees. For example, the crown angle  588  taken along a side cross sectional view positioned approximately 1.0 inch toward the heel  522  from the geometric center  540  of the strikeface  504  can be less than approximately 70 degrees, less than approximately 69 degrees, less than approximately 68 degrees, less than approximately 67 degrees, less than approximately 66 degrees, less than approximately 65 degrees, less than approximately 64 degrees, less than approximately 63 degrees, less than approximately 62 degrees, less than approximately 61 degrees, less than approximately 60 degrees, less than approximately 59 degrees. 
     Further still, in other embodiments, the crown angle  588  near the center of the club head  500  can be less than 75 degrees, less than 74 degrees, less than 73 degrees, less than 72 degrees, less than 71 degrees, less than approximately 70 degrees, less than approximately 69 degrees, less than approximately 68 degrees, less than approximately 67 degrees, less than approximately 66 degrees, less than approximately 65 degrees, less than approximately 64 degrees, less than approximately 63 degrees, less than approximately 62 degrees, less than approximately 61 degrees, less than approximately 60 degrees, less than approximately 59 degrees. For example, the crown angle  588  taken along a side cross sectional view positioned approximately at the geometric center  540  of the strikeface  504  can be less than approximately 70 degrees, less than approximately 69 degrees, less than approximately 68 degrees, less than approximately 67 degrees, less than approximately 66 degrees, less than approximately 65 degrees, less than approximately 64 degrees, less than approximately 63 degrees, less than approximately 62 degrees, less than approximately 61 degrees, less than approximately 60 degrees, less than approximately 59 degrees. 
     In many embodiments, reducing the crown angle  588  compared to current club heads generates a steeper crown or a crown positioned closer to the ground plane  1030  when the club head  500  is at an address position. Accordingly, the reduced crown angle  588  can result in a lower head CG position compared to a club head with a higher crown angle. 
     vi. Hosel Sleeve Weight 
     In some embodiments, the head CG height  174  and/or head CG depth  172  can be achieved by reducing the mass of the hosel sleeve  534 . Removing excess weight from the hosel sleeve  534  results in increased discretionary weight that can be strategically repositioned to regions of the club head  500  to achieve the desired low and back club head CG position. 
     Reducing the mass of the hosel sleeve  534  can be achieved by thinning the sleeve walls, reducing the height of the hosel sleeve  534 , reducing the diameter of the hosel sleeve  534 , and/or by introducing voids in the walls of the hosel sleeve  534 . In many embodiments, the mass of the hosel sleeve  534  can be less than 6 grams, less than 5.5 grams, less than 5.0 grams, less than 4.5 grams, or less than 4.0 grams. In many embodiments, the club head  500  having the reduced mass hosel sleeve  534  can result in a lower (close to the sole) and farther back (closer to the back end) club head CG position than a similar club head  500  with a heavier hosel sleeve. 
     B. Aerodynamic Drag 
     In many embodiments, the club head  500  comprises a low and back club head CG position and an increased club head moment of inertia, in combination with reduced aerodynamic drag. 
     In many embodiments, the club head  500  experiences an aerodynamic drag force less than approximately 1.3 lbf, less than 1.25 lbf, less than 1.2 lbf, less than 1.15 lbf, less than 1.1 lbf, less than 1.05 lbf, or less than 1.0 lbf when tested in a wind tunnel with a squared face and an air speed of 102 miles per hour (mph). In these or other embodiments, the club head  500  experiences an aerodynamic drag force less than approximately 1.3 lbf, less than 1.25 lbf, less than 1.2 lbf, less than 1.15 lbf, less than 1.1 lbf, less than 1.05 lbf, or less than 1.0 lbf when simulated using computational fluid dynamics with a squared face and an air speed of 102 miles per hour (mph). In these embodiments, the airflow experienced by the club head  500  having the squared face is directed at the strikeface  504  in a direction perpendicular to the X′Y′ plane. The club head  500  having reduced aerodynamic drag can be achieved using various means, as described below. 
     i. Crown Angle Height 
     In some embodiments, reducing the crown angle  588  to form a steeper crown and lower head CG position may result in an undesired increase in aerodynamic drag due to increased air flow separation over the crown during a swing. To prevent increased drag associated with a reduced crown angle  588 , a maximum crown height  604  can be increased. The maximum crown height  604  is the greatest distance between the surface of the crown  516  and the crown axis  1090  taken at any side cross sectional view of the club head  500  along a plane positioned parallel to the Y′Z′ plane. In many embodiments, a greater maximum crown height  604  results in the crown having a greater curvature. A greater curvature in the crown  516  moves the location of the air flow separation during a swing further back on the club head  500 . In other words, a greater curvature allows the airflow to stay attached to club head  500  for a longer distance along the crown  516  during a swing. Moving the airflow separation point back on the crown  516  can result in reduced aerodynamic drag and increased club head swing speeds, thereby resulting in increased ball speed and distance. 
     In many embodiments, the maximum crown height  404  can be greater than approximately 0.20 inch (5 mm), greater than approximately 0.30 inch (7.5 mm), greater than approximately 0.40 inch (10 mm), greater than approximately 0.50 inch (12.5 mm), greater than approximately 0.60 inch (15 mm), greater than approximately 0.70 inch (17.5 mm), greater than approximately 0.80 inch (20 mm), greater than approximately 0.90 inch (22.5 mm), or greater than approximately 1.0 inch (25 mm). Further, in other embodiments, the maximum crown height can be within the range of 0.20 inch (5 mm) to 0.60 inch (15 mm), or 0.40 inch (10 mm) to 0.80 inch (20 mm), or 0.60 inch (15 mm) to 1.0 inch (25 mm). For example, in some embodiments, the maximum crown height  404  can be approximately 0.52 inch (13.3 mm), approximately 0.54 inch (13.8 mm), approximately 0.59 inch (15 mm), approximately 0.65 inch (16.5 mm), or approximately 0.79 inch (20 mm). 
     ii. Transition Profiles 
     In many embodiments, the transition profiles of the club head  500  from the strikeface  504  to the crown  516 , the strikeface  504  to the sole  518 , and/or the crown  516  to the sole  518  along the back end  510  of the club head  500  can affect the aerodynamic drag on the club head  500  during a swing. 
     In some embodiments, the club head  500  having the top transition boundary defining the crown transition profile  590 , and the rear transition boundary defining the rear transition profile  596  further includes a sole transition boundary defining a sole transition profile  610 . The sole transition boundary extends between the front end  508  and the sole  518  from near the heel  520  to near the toe  522 . The sole transition boundary includes a sole transition profile  610  when viewed from a side cross sectional view taken along a plane parallel to the Y′Z′ plane. The side cross sectional view can be taken along any point of the club head  500  from near the heel  520  to near the toe  522 . The sole transition profile  610  defines a sole radius of curvature  612  extending from the front end  508  of the club head  500  where the contour departs from the roll radius and/or the bulge radius of the strikeface  504  to a sole transition point  614  indicating a change in curvature from sole radius of curvature  612  to the curvature of the sole  518 . In some embodiments, the sole radius of curvature  612  comprises a single radius of curvature extending from the bottom end  613  of the strikeface perimeter  542  near the sole  518  where the contour departs from the roll radius and/or the bulge radius of the strikeface  504  to a sole transition point  614  indicating a change in curvature from the sole radius of curvature  612  to a curvature of the sole  614 . 
     In many embodiments, the crown transition profile  590 , the sole transition profile  610 , and the rear transition profile  596  can be similar to the crown transition, sole transition, and rear transition profiles described in U.S. patent Ser. No. 15/233,486, entitled “Golf Club Head with Transition Profiles to Reduce Aerodynamic Drag.” Further, the front radius of curvature  592  can be similar to the first crown radius of curvature, the sole radius of curvature  612  can be similar to the first sole radius of curvature, and the rear radius of curvature  398  can be similar to the rear radius of curvature described U.S. patent Ser. No. 15/233,486, entitled “Golf Club Head with Transition Profiles to Reduce Aerodynamic Drag.” 
     In some embodiments, front radius of curvature  592  can range from approximately 0.18 to 0.30 inches (0.46 to 0.76 cm). Further, in other embodiments, the front radius of curvature  592  can be less than 0.40 inches (1.02 cm), less than 0.375 inches (0.95 cm), less than 0.35 inches (0.89 cm), less than 0.325 inches (0.83 cm), or less than 0.30 inches 0.76 cm). For example, the front radius of curvature  592  may be approximately 0.18 inches (0.46 cm), 0.20 inches (0.51 cm), 0.22 inches (0.66 cm), 0.24 inches (0.61 cm), 0.26 inches (0.66 cm), 0.28 inches (0.71 cm), or 0.30 inches (0.76 cm). 
     In some embodiments, the sole radius of curvature  612  can range from approximately 0.25 to 0.50 inches (0.76 to 1.27 cm). For example, the sole radius of curvature  612  can be less than approximately 0.5 inches (1.27 cm), less than approximately 0.475 inches (1.21 cm), less than approximately 0.45 inches (1.14 cm), less than approximately 0.425 inches (1.08 cm), or less than approximately 0.40 inches (1.02 cm). For further example, the sole radius of curvature  612  can be approximately 0.30 inches (0.76 cm), 0.35 inches (0.89 cm), 0.40 inches (1.02 cm), 0.45 inches (1.14 cm), or 0.50 inches (1.27 cm). 
     In some embodiments, the rear radius of curvature  598  can range from approximately 0.10 to 0.25 inches (0.25 to 0.64 cm). For example, the rear radius of curvature  598  can be less than approximately 0.3 inches (0.76 cm), less than approximately 0.275 inches (0.70 cm), less than approximately 0.25 inches (0.64 cm), less than approximately 0.225 inches (0.57 cm), or less than approximately 0.20 inches (0.51 cm). For further example, the rear radius of curvature  598  can be approximately 0.10 inches (0.25 cm), 0.15 inches (0.38 cm), 0.20 inches (0.51 cm), or 0.25 inches (0.64 cm). 
     iii. Turbulators 
     In some embodiments, the club head  500  can further include a plurality of turbulators  614 , as described in U.S. patent application Ser. No. 13/536,753, now U.S. Pat. No. 8,608,587, granted on Dec. 17, 2013, entitled “Golf Club Heads with Turbulators and Methods to Manufacture Golf Club Heads with Turbulators,” which is incorporated fully herein by reference. In many embodiments, the plurality of turbulators  614  disrupt the airflow thereby creating small vortices or turbulence inside the boundary layer to energize the boundary layer and delay separation of the airflow on the crown during a swing. 
     In some embodiments, the plurality of turbulators  614  can be adjacent to the crown transition point  794  of the club head  500 . The plurality of turbulators  614  project from an outer surface of the crown  508  and include a length extending between the front end  508  and the back end  510  of the club head  500 , and a width extending from the heel  520  to the toe  522  of the club head  500 . In many embodiments, the length of the plurality of turbulators is greater than the width. In some embodiments, the plurality of turbulators  614  can comprise the same width. In some embodiments, the plurality of turbulators  614  can vary in height profile. In some embodiments, the plurality of turbulators  614  can be higher toward the apex of the crown  516  than in comparison to the front of the crown  516 . In other embodiments, the plurality of turbulators  614  can be higher toward the front of the crown  516 , and lower in height toward the apex of the crown  516 . In other embodiments, the plurality of turbulators  614  can comprise a constant height profile. Further, in many embodiments, at least a portion of at least one turbulator is located between the strikeface  504  and an apex of the crown  516 , and the spacing between adjacent turbulators is greater than the width of each of the adjacent turbulators. 
     iv. Back Cavity 
     In some embodiments, the club head  500  can further include a cavity  620  located at the back end  510  and in the trailing edge  528  of the club head  500 . In many embodiments, the cavity can be similar to cavity  420  on club head  300 . Further, the cavity can be similar to the cavity described in U.S. patent application Ser. No. 14/882,092, entitled “Golf Club Heads with Aerodynamic Features and Related Methods.” In many embodiments, the cavity  620  can break the vortices generated behind golf club head  500  into smaller vortices to reduce the size of the wake and/or reduce drag. In some embodiments, breaking the vortices into smaller vortices can generate a region of high pressure behind golf club head  500 . In some embodiments, this region of high pressure can push golf club head  500  forward, reduce drag, and/or enhance the aerodynamic design of golf club head  500 . In many embodiments, the net effect of smaller vortices and reduced drag is an increase in the speed of golf club head  500 . This effect can lead to higher speeds at which a golf ball leaves strikeface after impact to increase ball travel distance. 
     In many embodiments, the cavity  620  can include a back wall  622 , similar to back wall  422 , that is oriented in a direction perpendicular to the X′Z′ plane and can include a width measured in a direction from the heel  520  to the toe  522 , a depth  624  (similar to depth  424  of cavity  420 ), and a height  626  (similar to height  426  of cavity  420 ). The width of the cavity  620  can be approximately 1.0 inches (approximately 2.54 centimeters (cm)) to approximately 8 inch (approximately 20.32 cm), approximately 1.0 inches (approximately 2.54 cm) to approximately 2.25 inches (approximately 5.72 cm), or approximately 1.75 inches (approximately 4.5 cm) to approximately 2.25 inches (approximately 5.72 cm). For example, the width of the cavity  620  can be approximately 2.0 inches (5.08 cm), 3.0 inches (7.62 cm), 4.0 inches (10.16 cm), 5.0 inches (12.7 cm), 6.0 inches (15.24 cm), or 7.0 inches (17.78 cm). In some embodiments, the width of the cavity  620  can remain constant from near the top of the cavity (toward the crown  516  of the club head  500 ) to near the bottom of the cavity (toward the sole  518  of the club head  500 ). In other embodiments, the width of the cavity can vary from near the top to near the bottom. In some embodiments, the width of the cavity can be largest near the top and smallest near the bottom. In other embodiments, the width of the cavity can vary according to any profile. For example, in other embodiments, the width of the cavity can be longest at the top, at the bottom, at the center, or at any other location extending from the top to the bottom of the cavity  620 . 
     The depth  624  of the cavity  620  can be approximately 0.025 inch (approximately 0.127 cm) to approximately 0.250 inch (approximately 0.635 cm), or approximately 0.025 inch (approximately 0.127 cm) to approximately 0.150 inch (approximately 0.381 cm). For example, the depth  624  of the cavity  620  can be approximately 0.1 inch (approximately 0.254 cm), or approximately 0.05 inch (approximately 0.127 cm). In some embodiments, the depth of the cavity can remain constant between the heel and the toe and/or between the top and the bottom of the cavity. In other embodiments, the depth of the cavity can vary between the heel and the toe and/or between the top and the bottom of the cavity. For example, the depth of the cavity can be the largest near the heel, near the toe, near the crown, near the sole, near the center, or at any combination of the described locations. 
     The height  626  of the cavity  620  can be measured in a direction from the crown  516  to the sole  518 . The height  626  of the cavity  620  can be approximately 0.19 inch (approximately 0.48 cm) to approximately 0.21 inch (approximately 0.53 cm). In some embodiments, the height  626  of the cavity  620  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.50 inch (approximately 1.27 cm). In some embodiments, the height  626  of the cavity  620  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.40 inch (approximately 1.02 cm). In some embodiments, the height  626  of the cavity  620  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.30 inch (approximately 0.76 cm). In some embodiments, the height  626  of the cavity  620  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.20 inch (approximately 0.51 cm). In some embodiments, the height of the cavity can remain constant between the heel and the toe of the cavity. In other embodiments, the height of the cavity can vary between the heel and the toe of the cavity. For example, the height of the cavity can be the largest near the heel, near the toe, near the center, or at any combination of the described locations. 
     v. Hosel Structure 
     In some embodiments, the hosel structure  530  can have a smaller outer diameter to reduce the aerodynamic drag on the club head  500  during a swing, compared to a similar club head having a larger diameter hosel structure. In many embodiments, the hosel structure  530  has an outer diameter less than 0.545 inches. For example, the hosel structure  530  can have an outer diameter less than 0.60 inches, less than 0.59 inches, less than 0.58 inches, less than 0.57 inches, less than 0.56 inches, less than 0.55 inches, less than 0.54 inches, less than 0.53 inches, less than 0.52, less than 0.51 inches, or less than 0.50 inches. In many embodiments, the outer diameter of the hosel structure  530  is reduced while maintaining adjustability of the loft angle and/or lie angle of the club head  500 . 
     vi. Projected Area 
     In many embodiments, the club head  500  further comprises a front projected area and a side projected area. The front projected area is the area of the club head  500  visible from the front view, as illustrated in  FIG. 1 , and projected on the X′Y′ plane. The side projected area is the area of the club head  500  visible from the side view and projected on the Y′Z′ plane. 
     In many embodiments, the front projected area of the club head  500  can be between 0.00400 m 2  and 0.00700 m 2 . For example, in the illustrated embodiment, the front projected area of the club head is 0.00655 m 2 . In other embodiments, the front projected area can be between 0.00400 m 2  and 0.00665 m 2 , between 0.00400 m 2  and 0.00675 m 2 , between 0.00400 m 2  and 0.00685 m 2 , or between 0.00400 m 2  and 0.00695 m 2 . 
     In many embodiments, the side projected area of the club head  500  can be between 0.00500 m 2  and 0.00650 m 2 . For example, in the illustrated embodiment, the front projected area of the club head is 0.00579 m 2 . In other embodiments, the front projected area can be between 0.00545 m 2  and 0.00565 m 2 , between 0.00535 m 2  and 0.00575 m 2 , between 0.00525 m 2  and 0.00585 m 2 , or between 0.00515 m 2  and 0.00595 m 2 . 
     C. Balance of CG Position, Moment of Inertia, and Aerodynamic Drag 
     In current golf club head design, increasing or maximizing the moment of inertia of the club head and/or the head CG position can adversely affect other performance characteristics of the club head, such as aerodynamic drag. The club head  500  described herein increases or maximizes the club head moment of inertia, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  500  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     In the examples of club head  300  and  500  described below, the aerodynamic drag of the club head is measured using computational fluid dynamic simulations with the front end of the club head oriented square into the airstream at an air speed of 102 miles per hour (mph). In other embodiments, the aerodynamic drag can be measured using other methods, such as using wind tunnel testing. 
     In many known golf club heads, increasing or maximizing the moment of inertia of the club head adversely affects aerodynamic drag.  FIGS. 10A-C  illustrate that for many known club heads having volume and/or loft angle similar to club head  300  or club head  500 , as the club head moment of inertia increases (to increase club head forgiveness), the force of drag during a swing increases (thereby reducing swing speed and ball distance). 
     For example, referring to  FIG. 10A , for many known club heads, as the moment of inertia about the x-axis increases, the force of drag increases. For further example, referring to  FIG. 10B , for many known club heads, as the moment of inertia about the y-axis increases, the force of drag increases. For further example referring to  FIG. 10C , for many known club heads, as the combined moment of inertia (i.e. the sum of the moment of inertia about the x-axis and the moment of inertia about the y-axis) increases, the force of drag increases. 
     The club head  300 ,  500  described herein increases or maximizes the club head moment of inertia compared to known club heads having similar volume and/or loft angle, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  300 ,  500  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     In many embodiments, referring to  FIG. 11 , the club head  300 ,  500  satisfies one or more of the following relations, such that the combined moment of inertia (I xx +I yy ) of the club head is increased, while maintaining or reducing the drag force (F D ) on the club head, compared to known golf club heads having similar volume and/or loft angle. Specifically,  FIG. 11A  correlates to Relation 3,  FIG. 11B  correlates to Relation 4, and  FIG. 11C  correlates to Relation 
     
       
         
           
             
               
                 
                   
                     
                       
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     For example, in many embodiments, the club head  300 ,  500  satisfies Relation 3, and has a combined moment of inertia greater than 9000 g·cm 2 . In other embodiments, the club head  300 ,  500  can satisfy Relation 3, and can have a combined moment of inertia greater than 9010 g·cm 2 , greater than 9025 g·cm 2 , greater than 9050 g·cm 2 , greater than 9075 g·cm 2 , greater than 10000 g·cm 2 , greater than 10250 g·cm 2 , greater than 10500 g·cm 2 , greater than 10750 g·cm 2 , or greater than 11000 g·cm 2 . 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 3, and has a drag force less than 1.16 lbf. In other embodiments, the club head  300 ,  500  can satisfy Relation 3, and can have a drag force less than 1.15 lbf, less than 1.10 lbf, less than 1.00 lbf, less than 0.900 lbf, less than 0.800 lbf, less than 0.75 lbf, less than 0.700 lbf, less than 0.600 lbf, or less than 0.500 lbf. 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 4, and has a combined moment of inertia greater than 9000 g·cm 2 . In other embodiments, the club head  300 ,  500  can satisfy Relation 4, and can have a combined moment of inertia greater than 9010 g·cm 2 , greater than 9025 g·cm 2 , greater than 9050 g·cm 2 , greater than 9075 g·cm 2 , greater than 10000 g·cm 2 , greater than 10250 g·cm 2 , greater than 10500 g·cm 2 , greater than 10750 g·cm 2 , or greater than 11000 g·cm 2 . 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 4, and has a drag force less than 1.16 lbf. In other embodiments, the club head  300 ,  500  can satisfy Relation 4, and can have a drag force less than 1.15 lbf, less than 1.10 lbf, less than 1.00 lbf, less than 0.900 lbf, less than 0.800 lbf, less than 0.75 lbf, less than 0.700 lbf, less than 0.600 lbf, or less than 0.500 lbf. 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 5, and has a combined moment of inertia greater than 9000 g·cm 2 . In other embodiments, the club head  300 ,  500  can satisfy Relation 5, and can have a combined moment of inertia greater than 9010 g·cm 2 , greater than 9025 g·cm 2 , greater than 9050 g·cm 2 , greater than 9075 g·cm 2 , greater than 10000 g·cm 2 , greater than 10250 g·cm 2 , greater than 10500 g·cm 2 , greater than 10750 g·cm 2 , or greater than 11000 g·cm 2 . 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 5, and has a drag force less than 1.16 lbf. In other embodiments, the club head  300 ,  500  can satisfy Relation 5, and can have a drag force less than 1.15 lbf, less than 1.10 lbf, less than 1.00 lbf, less than 0.900 lbf, less than 0.800 lbf, less than 0.75 lbf, less than 0.700 lbf, less than 0.600 lbf, or less than 0.500 lbf. 
     i. CG Position and Aerodynamic Drag 
     In many known golf club heads, shifting the CG position farther back to increase launch angle of a golf ball and/or to increase club head inertia, can adversely affect other performance characteristics of the club head, such as aerodynamic drag.  FIG. 12  illustrates that for many known club heads having a volume and/or loft angle similar to club head  300  or club head  500 , as the club head CG depth increases (to increase club head forgiveness and or launch angle), the force of drag during a swing increases (thereby reducing swing speed and ball distance). For example, referring to  FIG. 12 , for many known club heads, as the head CG depth increases, the force of drag on the club head increases. 
     The club head  300 ,  500  described herein increases or maximizes the club head CG depth compared to known club heads having similar volume and/or loft angle, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  300 ,  500  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     In many embodiments, referring to  FIG. 13 , the club head  300 ,  500  satisfies one or more of the following relations, such that the head CG depth (CG D ) is increased, while maintaining or reducing the drag force (F D ) on the club head, compared to known golf club heads. Specifically,  FIG. 13A  correlates to Relation 6,  FIG. 13B  correlates to Relation 7, and  FIG. 13C  correlates to Relation 8. 
     
       
         
           
             
               
                 
                   
                     
                       
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     For example, in many embodiments, the club head  300 ,  500  satisfies Relation 6, and has a head CG depth greater than 1.65 inches. In other embodiments, the club head  300 ,  500  can satisfy Relation 6, and can have a head CG depth greater than 1.60 inches, greater than 1.62 inches, greater than 1.64 inches, greater than 1.68 inches, greater than 1.70 inches, greater than 1.72 inches, greater than 1.74 inches, greater than 1.76 inches, greater than 1.78 inches, greater than 1.80 inches, greater than 1.85 inches, or greater than 1.90 inches. 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 6, and has a drag force less than 1.16 lbf. In other embodiments, the club head  300 ,  500  can satisfy Relation 6, and can have a drag force less than 1.15 lbf, less than 1.10 lbf, less than 1.00 lbf, less than 0.900 lbf, less than 0.800 lbf, less than 0.75 lbf, less than 0.700 lbf, less than 0.600 lbf, or less than 0.500 lbf. 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 7, and has a combined moment of inertia greater than 9000 g·cm 2 . In other embodiments, the club head  300 ,  500  can satisfy Relation 7, and can have a head CG depth greater than 1.60 inches, greater than 1.62 inches, greater than 1.64 inches, greater than 1.68 inches, greater than 1.70 inches, greater than 1.72 inches, greater than 1.74 inches, greater than 1.76 inches, greater than 1.78 inches, greater than 1.80 inches, greater than 1.85 inches, or greater than 1.90 inches. 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 7, and has a drag force less than 1.16 lbf. In other embodiments, the club head  300 ,  500  can satisfy Relation 7, and can have a drag force less than 1.15 lbf, less than 1.10 lbf, less than 1.00 lbf, less than 0.900 lbf, less than 0.800 lbf, less than 0.75 lbf, less than 0.700 lbf, less than 0.600 lbf, or less than 0.500 lbf. 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 8, and has a combined moment of inertia greater than 9000 g·cm 2 . In other embodiments, the club head  300 ,  500  can satisfy Relation 8, and can have a head CG depth greater than 1.60 inches, greater than 1.62 inches, greater than 1.64 inches, greater than 1.68 inches, greater than 1.70 inches, greater than 1.72 inches, greater than 1.74 inches, greater than 1.76 inches, greater than 1.78 inches, greater than 1.80 inches, greater than 1.85 inches, or greater than 1.90 inches. 
     For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 8, and has a drag force less than 1.16 lbf. In other embodiments, the club head  300 ,  500  can satisfy Relation 8, and can have a drag force less than 1.15 lbf, less than 1.10 lbf, less than 1.00 lbf, less than 0.900 lbf, less than 0.800 lbf, less than 0.75 lbf, less than 0.700 lbf, less than 0.600 lbf, or less than 0.500 lbf. 
     ii. Moment of Inertia and CG Depth 
     Referring to  FIG. 14 , the combined moment of inertia and/or head CG depth many known golf club heads are limited. For example, many known golf club heads having a volume and/or loft angle similar to club head  300  or club head  500  have a head CG depth less than 1.6 inches and a combined moment of inertia less than 8900 g·cm 2 . The club head  300 ,  500  described herein has a greater head CG depth and a greater combined moment of inertia than known club heads having similar volume and/or loft angle, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  300 ,  500  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     For example, in many embodiments the club head  300 ,  500  has a head CG depth greater than 1.65 inches and a combined moment of inertia greater than 9000 g·cm 2 . In other embodiments, the club head  300 ,  500  can have a head CG depth greater than 1.60 inches, greater than 1.62 inches, greater than 1.64 inches, greater than 1.68 inches, greater than 1.70 inches, greater than 1.72 inches, greater than 1.74 inches, greater than 1.76 inches, greater than 1.78 inches, greater than 1.80 inches, greater than 1.85 inches, or greater than 1.90 inches. Further, in other embodiments, the club head  300 ,  500  can have a combined moment of inertia greater than 9010 g·cm 2 , greater than 9025 g·cm 2 , greater than 9050 g·cm 2 , greater than 9075 g·cm 2 , greater than 10000 g·cm 2 , greater than 10250 g·cm 2 , greater than 10500 g·cm 2 , greater than 10750 g·cm 2 , or greater than 11000 g·cm 2 . 
     III. Fairway Wood-Type Club Head 
     According to another embodiment as illustrated in  FIGS. 15-22 , a golf club head  700  can comprise a fairway wood-type club head. In many embodiments, club head  700  comprises the same or similar parameters as club head  100 , wherein the parameters are described with the club head  100  reference numbers plus  600 . 
     In many embodiments, the loft angle of the club head  700  is less than approximately 35 degrees, less than approximately 34 degrees, less than approximately 33 degrees, less than approximately 32 degrees, less than approximately 31 degrees, or less than approximately 30 degrees. Further, in many embodiments, the loft angle of the club head  700  is greater than approximately 12 degrees, greater than approximately 13 degrees, greater than approximately 14 degrees, greater than approximately 15 degrees, greater than approximately 16 degrees, greater than approximately 17 degrees, greater than approximately 18 degrees, greater than approximately 19 degrees, or greater than approximately 20 degrees. For example, in some embodiments, the loft angle of the club head  700  can be between 12 degrees and 35 degrees, between 15 degrees and 35 degrees, between 20 degrees and 35 degrees, or between 12 degrees and 30 degrees. 
     In many embodiments, the volume of the club head  700  is less than approximately 400 cc, less than approximately 375 cc, less than approximately 350 cc, less than approximately 325 cc, less than approximately 300 cc, less than approximately 275 cc, less than approximately 250 cc, less than approximately 225 cc, or less than approximately 200 cc. In some embodiments, the volume of the club head can be approximately 150 cc-200 cc, approximately 150 cc-250 cc, approximately 150 cc-300 cc, approximately 150 cc-350 cc, approximately 150 cc-400 cc, approximately 200 cc-300 cc, approximately 200 cc-350 cc, approximately 300 cc-400 cc, approximately 325 cc-400 cc, approximately 350 cc-400 cc, approximately 250 cc-400 cc, approximately 250-350 cc, or approximately 275-375 cc. In other embodiments, the golf club head  700  can comprise any type of golf club head having a loft angle and volume as described herein. 
     The length  762  of the club head  700  can be measured from the farthest extent of the club head  700  from the heel  720  to the toe  722 , in a direction parallel to the X′ axis  1052 , when viewed from the front view ( FIG. 15 ). In many embodiments, the length  762  of the club head  700  is can be between 3.5 inches and 4.75 inches, between 4.0 inches and 4.85 inches, between 3.5 inches and 5.0 inches, or between 4.0 inches and 4.5 inches. In many embodiments as illustrated in  FIG. 16 , the depth  760  of the club head  700  is at least 0.70 inches less than the length  362  of the club head  300 . For example, in many embodiments, the depth  760  of the club head  700  can be between 2.75 inches and 4.5 inches, between 3.0 inches and 4.0 inches, between 3.0 inches and 3.75 inches, or between 3.0 inches and 4.85 inches. 
     The height  764  of the club head  700  can be measured as the furthest extend of the club head  700  from the crown  716  to the sole  718 , in a direction parallel to the Y′ axis  1062 , when viewed from the front view ( FIG. 15 ). In many embodiments, the height  764  of the club head  700  is less than approximately 2.0 inches. In other embodiments, the height  764  of the club head  700  is less than 2.5 inches, less than 2.4 inches, less than 2.3 inches, less than 2.2 inches, less than 2.1 inches, less than 1.9 inches, or less than 1.8 inches. For example, in some embodiments, the height  764  of the club head  700  can be between 1.3-1.7 inches, between 1.5-2.0 inches, between 1.75-2.5 inches, between 1.75-2.0 inches, or between 2.0-2.5 inches. Further, in many embodiments, the face height  744  of the club head can be approximately 0.5 inches (12.7 mm) to approximately 2.0 inches (50.8 mm). Further still, in many embodiments, the club head  700  can comprise a mass between 185 grams and 250 grams. 
     The club head  700  further comprises a balance of various additional parameters, such as head CG position, club head moment of inertia, and aerodynamic drag, to provide both improved impact performance characteristics (e.g. spin, launch angle, speed, forgiveness) and swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact). In many embodiments, the balance of parameters described below provides improved impact performance while maintaining or improving swing performance characteristics. Further, in many embodiments, the balance of parameters described below provides improved swing performance characteristics while maintaining or improving impact performance characteristics. 
     A. Center of Gravity Position and Moment of Inertia 
     In many embodiments, a low and back club head CG and increased moment of inertia can be achieved by increasing discretionary weight and repositioning discretionary weight in regions of the club head having maximized distances from the head CG. Increasing discretionary weight can be achieved by thinning the crown and/or using optimized materials, as described above relative to the head CG position. Repositioning discretionary weight to maximize the distance from the head CG can be achieved using removable weights, embedded weights, or a steep crown angle, as described above relative to the head CG position. 
     In many embodiments, the club head  700  comprises a crown-to-sole moment of inertia I xx  greater than approximately 1500 g·cm 2 , greater than approximately 1600 g·cm 2 , greater than approximately 1600 g·cm 2 , greater than approximately 1650 g·cm 2 , greater than approximately 1700 g·cm 2 , greater than approximately 1750 g·cm 2 , greater than approximately 1800 g·cm 2 , greater than approximately 1850 g·cm 2 , greater than approximately 1900 g·cm 2 , greater than approximately 1950 g·cm 2 , greater than approximately 2000 g·cm 2 , greater than approximately 2100 g·cm 2 , greater than approximately 2200 g·cm 2 , greater than approximately 2300 g·cm 2 , greater than approximately 2400 g·cm 2 , greater than approximately 2500 g·cm 2 , greater than approximately 2600 g·cm 2 , greater than approximately 2700 g·cm 2 , or greater than approximately 2800 g·m 2 . 
     In many embodiments, the club head  700  comprises a heel-to-toe moment of inertia I yy  greater than approximately 3000 g·cm 2 , greater than approximately 3100 g·cm 2 , greater than approximately 3200 g·cm 2 , greater than approximately 3250 g·cm 2 , greater than approximately 3300 g·cm 2 , greater than approximately 3400 g·cm 2 , greater than approximately 3500 g·cm 2 , greater than approximately 3600 g·cm 2 , greater than approximately 3750 g·cm 2 , greater than approximately 4000 g·cm 2 , greater than approximately 4250 g·cm 2 , greater than approximately 4500 g·cm 2 , greater than approximately 4750 g·cm 2 , greater than approximately 5000 g·cm 2 , greater than approximately 5250 g·cm 2 , greater than approximately 5500 g·cm 2 , greater than approximately 5750 g·cm 2 , greater than approximately 6000 g·cm 2 , greater than approximately 6250 g·cm 2 , greater than approximately 6500 g·cm 2 , greater than approximately 6750 g·cm 2 , or greater than approximately 7000 g·cm 2 . 
     In many embodiments, the club head  700  comprises a combined moment of inertia (i.e. the sum of the crown-to-sole moment of inertia I xx  and the heel-to-toe moment of inertia I yy ) greater than 4900 g·cm 2 , greater than 4950 g·cm 2 , greater than 5000 g·cm 2 , greater than 5100 g·cm 2 , greater than 5200 g·cm 2 , greater than 5300 g·cm 2 , greater than 5400 g·cm 2 , greater than 5500 g·cm 2 , greater than 5600 g·cm 2 , greater than 5700 g·cm 2 , greater than 5800 g·cm 2 , greater than 5900 g·cm 2 , or greater than 6000 g·cm 2 . 
     In many embodiments, the club head  700  comprises a head CG height  774  less than approximately 0.50 inches, less than approximately 0.475 inches, less than approximately 0.45 inches, less than approximately 0.425 inches, less than approximately 0.40 inches, less than approximately 0.35 inches, less than approximately 0.30 inches, less than approximately 0.25 inches, less than approximately 0.20 inches, less than 0.15 inches, or less than 0.10 inches. Further, in many embodiments, the club head  700  comprises a head CG height  774  having an absolute value less than approximately 0.50 inches, less than approximately 0.475 inches, less than approximately 0.45 inches, less than approximately 0.425 inches, less than approximately 0.40 inches, less than approximately 0.35 inches, less than approximately 0.30 inches, or less than approximately 0.25 inches. 
     In many embodiments, the club head  700  comprises a head CG depth  772  greater than approximately 1.0 inches, greater than approximately 1.1 inches, greater than approximately 1.22 inches, greater than approximately 1.2 inches, greater than approximately 1.3 inches, greater than approximately 1.4 inches, greater than approximately 1.5 inches, greater than approximately 1.6 inches, greater than approximately 1.7 inches, or greater than approximately 1.8 inches. 
     The club head  700  having the reduced head CG height  774  can reduce the backspin of a golf ball on impact compared to a similar club head having a higher head CG height. In many embodiments, reduced backspin can increase both ball speed and travel distance for improve club head performance. Further, the club head  700  having the increased head CG depth  772  can increase the heel-to-toe moment of inertia compared to a similar club head having a head CG depth closer to the strikeface. Increasing the heel-to-toe moment of inertia can increase club head forgiveness on impact to improve club head performance. Further still, the club head  700  having the increased head CG depth  772  can increase launch angle of a golf ball on impact by increasing the dynamic loft of the club head at delivery, compared to a similar club head having a head CG depth closer to the strikeface. 
     The head CG height  774  and/or head CG depth  772  can be achieved by reducing weight of the club head in various regions, thereby increasing discretionary weight, and repositioning discretionary weight in strategic regions of the club head to shift the head CG lower and farther back. Various means to reduce and reposition club head weight are described below. 
     i. Thin Regions 
     In some embodiments, the head CG height  772  and/or head CG depth  774  can be achieved by thinning various regions of the club head to remove excess weight. Removing excess weight results in increased discretionary weight that can be strategically repositioned to regions of the club head  700  to achieve the desired low and back club head CG position. 
     In many embodiments, the club head  700  can have one or more thin regions. The one or more thin regions can be similar or identical to the one or more thin regions  376  of club head  300 , or the one or more thin regions of club head  500 . The one or more thin regions can be positioned on the strikeface  704 , the body  702 , or a combination of the strikeface  704  and the body  702 . Further, the one or more thin regions can be positioned on any region of the body  702 , including the crown  716 , the sole  718 , the heel  720 , the toe  722 , the front end  708 , the back end  710 , the skirt  728 , or any combination of the described positions. For example, in some embodiments, the one or more thin regions can be positioned on the crown  716 . For further example, the one or more thin regions can be positioned on a combination of the strikeface  704  and the crown  716 . For further example, the one or more thin regions can be positioned on a combination of the strikeface  704 , the crown  716 , and the sole  718 . For further example, the entire body  702  and/or the entire strikeface  704  can comprise a thin region. 
     In embodiments where one or more thin regions are positioned on the strikeface  716 , the thickness of the strikeface  704  can vary defining a maximum strikeface thickness and a minimum strikeface thickness. In these embodiments, the minimum strikeface thickness can be less than 0.10 inches, less than 0.09 inches, less than 0.08 inches, less than 0.07 inches, less than 0.06 inches, less than 0.05 inches, less than 0.04 inches, less than 0.03 inches, or less than 0.02 inches. In these or other embodiments, the maximum strikeface thickness can be less than 0.20 inches, less than 0.19 inches, less than 0.18 inches, less than 0.17 inches, less than 0.16 inches, less than 0.15 inches, less than 0.14 inches, less than 0.13 inches, less than 0.12 inches, less than 0.11 inches, or less than 0.10 inches. 
     In embodiments where one or more thin regions are positioned on the body  302 , the thin regions can comprise a thickness less than approximately 0.022 inches. In other embodiments, the thin regions comprise a thickness less than 0.025 inches, less than 0.020 inches, less than 0.019 inches, less than 0.018 inches, less than 0.017 inches, less than 0.016 inches, less than 0.015 inches, less than 0.014 inches, less than 0.013 inches, less than 0.012 inches, or less than 0.010 inches. For example, the thin regions can comprise a thickness between approximately 0.010-0.025 inches, between approximately 0.013-0.022 inches, between approximately 0.014-0.020 inches, between approximately 0.015-0.020 inches, between approximately 0.016-0.020 inches, between approximately 0.017-0.020 inches, or between approximately 0.018-0.020 inches. 
     In the illustrated embodiment, the thin regions vary in shape and position and cover approximately 25% of the surface area of club head  700 . In other embodiments, the thin regions can cover approximately 20-30%, approximately 15-35%, approximately 15-25%, approximately 10-25%, approximately 15-30%, or approximately 20-50% of the surface area of club head  700 . Further, in other embodiments, the thin regions can cover up to 5%, up to 10%, up to 15%, up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, or up to 50% of the surface area of club head  700 . 
     In many embodiments, the crown  716  comprises one or more thin regions, such that approximately 51% of the surface area of the crown  716  comprises thin regions. In other embodiments, the crown  716  comprises one or more thin regions, such that up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, up to 50%, up to 55%, up to 60%, up to 65%, up to 70%, up to 75%, up to 80%, up to 85%, or up to 90% of the crown  716  comprises thin regions. For example, in some embodiments, approximately 40-60% of the crown  716  can comprise thin regions. For further example, in other embodiments, approximately 50-100%, approximately 40-90%, approximately 35-65%, approximately 30-70%, or approximately 25-75% of the crown can comprise thin regions. In some embodiments, the crown  716  can comprise one or more thin regions, wherein each of the one or more thin regions become thinner in a gradient fashion. In this exemplary embodiment, the one or more thin regions of the crown  716  extend in a heel-to-toe direction, and each of the one or more thin regions decrease in thickness in a direction from the strikeface  704  toward the back end  710 . 
     In many embodiments, the sole  718  comprises one or more thin regions, such that approximately 64% of the surface area of the sole  718  comprises thin regions. In other embodiments, the sole  718  comprises one or more thin regions, such that up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, up to 50%, up to 55%, up to 60%, up to 65%, up to 70%, up to 75%, up to 80%, up to 85%, or up to 90% of the sole  718  comprises thin regions. For example, in some embodiments, approximately 40-60% of the sole  718  can comprise thin regions. For further example, in other embodiments, approximately 50-100%, approximately 40-90%, approximately 35-65%, approximately 30-70%, or approximately 25-75% of the sole  718  can comprise thin regions. 
     The thinned regions can comprise any shape, such as circular, triangular, square, rectangular, ovular, or any other polygon or shape with at least one curved surface. Further, one or more thinned regions can comprise the same shape as or a different shape than the remaining thinned regions. 
     In many embodiments, club head  700  having thin regions can be manufacturing using centrifugal casting. In these embodiments, centrifugal casting allows the club head  700  to have thinner walls than a club head manufactured using conventional casting. In other embodiments, portions of the club head  700  having thin regions can be manufactured using other suitable methods, such as stamping, forging, or machining. In embodiments where portions of the club head  700  having thin regions are manufactured using stamping, forging, or machining, the portions of the club head  700  can be coupled using epoxy, tape, welding, mechanical fasteners, or other suitable methods. 
     ii. Optimized Materials 
     In some embodiments, the strikeface  704  and/or the body  702  can comprise an optimized material having increased specific strength and/or increased specific flexibility. The specific flexibility is measured as a ratio of the yield strength to the elastic modulus of the optimized material. Increasing specific strength and/or specific flexibility can allow portions of the club head to be thinned, while maintaining durability. 
     In some embodiments, the first material of the strikeface  704  can be an optimized material, as described in U.S. Provisional Patent Appl. No. 62/399,929, entitled “Golf Club Heads with Optimized Material Properties.” In these or other embodiments, the first material comprising an optimized titanium alloy can have a specific strength greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 910,000 PSI/lb/in 3  (227 MPa/g/cm 3 ), greater than or equal to approximately 920,000 PSI/lb/in 3  (229 MPa/g/cm 3 ), greater than or equal to approximately 930,000 PSI/lb/in 3  (232 MPa/g/cm 3 ), greater than or equal to approximately 940,000 PSI/lb/in 3  (234 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 960,000 PSI/lb/in 3  (239 MPa/g/cm 3 ), greater than or equal to approximately 970,000 PSI/lb/in 3  (242 MPa/g/cm 3 ), greater than or equal to approximately 980,000 PSI/lb/in 3  (244 MPa/g/cm 3 ), greater than or equal to approximately 990,000 PSI/lb/in 3  (247 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), greater than or equal to approximately 1,100,000 PSI/lb/in 3  (274 MPa/g/cm 3 ), or greater than or equal to approximately 1,150,000 PSI/lb/in 3  (286 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the first material comprising an optimized titanium alloy can have a specific flexibility greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0091, greater than or equal to approximately 0.0092, greater than or equal to approximately 0.0093, greater than or equal to approximately 0.0094, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0096, greater than or equal to approximately 0.0097, greater than or equal to approximately 0.0098, greater than or equal to approximately 0.0099, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, or greater than or equal to approximately 0.0120. 
     In these or other embodiments, the first material comprising an optimized steel alloy can have a specific strength greater than or equal to approximately 650,000 PSI/lb/in 3  (162 MPa/g/cm 3 ), greater than or equal to approximately 700,000 PSI/lb/in 3  (174 MPa/g/cm 3 ), greater than or equal to approximately 750,000 PSI/lb/in 3  (187 MPa/g/cm 3 ), greater than or equal to approximately 800,000 PSI/lb/in 3  (199 MPa/g/cm 3 ), greater than or equal to approximately 810,000 PSI/lb/in 3  (202 MPa/g/cm 3 ), greater than or equal to approximately 820,000 PSI/lb/in 3  (204 MPa/g/cm 3 ), greater than or equal to approximately 830,000 PSI/lb/in 3  (207 MPa/g/cm 3 ), greater than or equal to approximately 840,000 PSI/lb/in 3  (209 MPa/g/cm 3 ), greater than or equal to approximately 850,000 PSI/lb/in 3  (212 MPa/g/cm 3 ), greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), greater than or equal to approximately 1,100,000 PSI/lb/in 3  (274 MPa/g/cm 3 ), greater than or equal to approximately 1,115,000 PSI/lb/in 3  (278 MPa/g/cm 3 ), or greater than or equal to approximately 1,120,000 PSI/lb/in 3  (279 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the first material comprising an optimized steel alloy can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0065, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, greater than or equal to approximately 0.0120, greater than or equal to approximately 0.0125, greater than or equal to approximately 0.0130, greater than or equal to approximately 0.0135, greater than or equal to approximately 0.0140, greater than or equal to approximately 0.0145, or greater than or equal to approximately 0.0150. 
     In these embodiments, the increased specific strength and/or increased specific flexibility of the optimized first material allow the strikeface  704 , or portions thereof, to be thinned, as described above, while maintaining durability. Thinning of the strikeface  704  can reduce the weight of the strikeface  704 , thereby increasing discretionary weight to be strategically positioned in other areas of the club head  700  to position the head CG low and back and/or increase the club head moment of inertia. 
     In some embodiments, the second material of the body  702  can be an optimized material, as described in U.S. Provisional Patent Appl. No. 62/399,929, entitled “Golf Club Heads with Optimized Material Properties.” In these or other embodiments, the second material comprising an optimized titanium alloy can have a specific strength greater than or equal to approximately 730,500 PSI/lb/in 3  (182 MPa/g/cm 3 ). For example, the specific strength of the optimized titanium alloy can be greater than or equal to approximately 650,000 PSI/lb/in 3  (162 MPa/g/cm 3 ), greater than or equal to approximately 700,000 PSI/lb/in 3  (174 MPa/g/cm 3 ), greater than or equal to approximately 750,000 PSI/lb/in 3  (187 MPa/g/cm 3 ), greater than or equal to approximately 800,000 PSI/lb/in 3  (199 MPa/g/cm 3 ), greater than or equal to approximately 850,000 PSI/lb/in 3  (212 MPa/g/cm 3 ), greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), or greater than or equal to approximately 1,100,000 PSI/lb/in 3  (272 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the second material comprising an optimized titanium alloy can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0065, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, or greater than or equal to approximately 0.0120. 
     In these or other embodiments, the second material comprising an optimized steel can have a specific strength greater than or equal to approximately 500,000 PSI/lb/in 3  (125 MPa/g/cm 3 ), greater than or equal to approximately 510,000 PSI/lb/in 3  (127 MPa/g/cm 3 ), greater than or equal to approximately 520,000 PSI/lb/in 3  (130 MPa/g/cm 3 ), greater than or equal to approximately 530,000 PSI/lb/in 3  (132 MPa/g/cm 3 ), greater than or equal to approximately 540,000 PSI/lb/in 3  (135 MPa/g/cm 3 ), greater than or equal to approximately 550,000 PSI/lb/in 3  (137 MPa/g/cm 3 ), greater than or equal to approximately 560,000 PSI/lb/in 3  (139 MPa/g/cm 3 ), greater than or equal to approximately 570,000 PSI/lb/in 3  (142 MPa/g/cm 3 ), greater than or equal to approximately 580,000 PSI/lb/in 3  (144 MPa/g/cm 3 ), greater than or equal to approximately 590,000 PSI/lb/in 3  (147 MPa/g/cm 3 ), greater than or equal to approximately 600,000 PSI/lb/in 3  (149 MPa/g/cm 3 ), greater than or equal to approximately 625,000 PSI/lb/in 3  (156 MPa/g/cm 3 ), greater than or equal to approximately 675,000 PSI/lb/in 3  (168 MPa/g/cm 3 ), greater than or equal to approximately 725,000 PSI/lb/in 3  (181 MPa/g/cm 3 ), greater than or equal to approximately 775,000 PSI/lb/in 3  (193 MPa/g/cm 3 ), greater than or equal to approximately 825,000 PSI/lb/in 3  (205 MPa/g/cm 3 ), greater than or equal to approximately 875,000 PSI/lb/in 3  (218 MPa/g/cm 3 ), greater than or equal to approximately 925,000 PSI/lb/in 3  (230 MPa/g/cm 3 ), greater than or equal to approximately 975,000 PSI/lb/in 3  (243 MPa/g/cm 3 ), greater than or equal to approximately 1,025,000 PSI/lb/in 3  (255 MPa/g/cm 3 ), greater than or equal to approximately 1,075,000 PSI/lb/in 3  (268 MPa/g/cm 3 ), or greater than or equal to approximately 1,125,000 PSI/lb/in 3  (280 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the second material comprising an optimized steel can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0062, greater than or equal to approximately 0.0064, greater than or equal to approximately 0.0066, greater than or equal to approximately 0.0068, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0072, greater than or equal to approximately 0.0076, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0084, greater than or equal to approximately 0.0088, greater than or equal to approximately 0.0092, greater than or equal to approximately 0.0096, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, greater than or equal to approximately 0.0120, greater than or equal to approximately 0.0125, greater than or equal to approximately 0.0130, greater than or equal to approximately 0.0135, greater than or equal to approximately 0.0140, greater than or equal to approximately 0.0145, or greater than or equal to approximately 0.0150. 
     In these embodiments, the increased specific strength and/or increased specific flexibility of the optimized second material allow the body  702 , or portions thereof, to be thinned, while maintaining durability. Thinning of the body  702  can reduce club head weight, thereby increasing discretionary weight to be strategically positioned in other areas of the club head  700  to position the head CG low and back and/or increase the club head moment of inertia. 
     iii. Removable Weights 
     In some embodiments, the club head  700  can include one or more weight structures  780  comprising one or more removable weights  782 . The one or more weight structures  780  and/or the one or more removable weights  782  can be located towards the sole  718  and towards the back end  710 , thereby positioning the discretionary weight on the sole  718  and near the back end  710  of the club head  700  to achieve a low and back head CG position. In many embodiments, the one or more weight structures  780  removably receive the one or more removable weights  782 . In these embodiments, the one or more removable weights  782  can be coupled to the one or more weight structures  780  using any suitable method, such as a threaded fastener, an adhesive, a magnet, a snap fit, or any other mechanism capable of securing the one or more removable weights  782  to the one or more weight structures  780 . 
     The weight structure  780  and/or removable weight  782  can be located relative to a clock grid  2000  (illustrated in  FIG. 17 ), which can be aligned with respect to the strikeface  704  when viewed from a top view. The clock grid comprises at least a 12 o&#39;clock ray, a 3 o&#39;clock ray, a 4 o&#39;clock ray, a 5 o&#39;clock ray, a 6 o&#39;clock ray, a 7 o&#39;clock ray, a 8 o&#39;clock ray, and a 9 o&#39;clock ray. For example, the clock grid  2000  comprises a 12 o&#39;clock ray  2012 , which is aligned with the geometric center  740  of the strikeface  704 . The 12 o&#39;clock ray  2012  is orthogonal to the X′Y′ plane. Clock grid  2000  can be centered along 12 o&#39;clock ray  2012 , at a midpoint between the front end  708  and back end  710  of the club head  700 . In the same or other examples, clock grid centerpoint  2010  can be centered proximate to a geometric centerpoint of golf club head  700  when viewed from a bottom view ( FIG. 17 ). The clock grid  2000  also comprises a 3 o&#39;clock ray  2003  extending towards the heel  720 , and a 9 o&#39;clock ray  2009  extending towards the toe  722  of the club head  700 . 
     A weight perimeter  784  of the weight structure  780  is located in the present embodiment towards the back end  710 , at least partially bounded between a 4 o&#39;clock ray  2004  and 8 o&#39;clock ray  2008  of clock grid  2000 , while a weight center  786  of a removable weight  782  positioned within weight structure  780  is located between a 5 o&#39;clock ray  2005  and a 7 o&#39;clock ray  2007 . In examples such as the present one, the weight perimeter  784  is fully bounded between the 4 o&#39;clock ray  2004  and the 8 o&#39;clock ray  2008 . Although the weight perimeter  784  is defined external to the club head  700  in the present example, there can be other examples where the weight perimeter  784  may extend into an interior of, or be defined within, the club head  700 . In some examples, the location of the weight structure  780  can be established with respect to a broader area. For instance, in such examples, the weight perimeter  784  of the weight structure  780  can be located towards the back end, at least partially bounded between the 4 o&#39;clock ray  2004  and 9 o&#39;clock ray  2009  of the clock grid  2000 , while the weight center  786  can be located between the 5 o&#39;clock ray  2005  and 8 o&#39;clock ray  2008 . 
     In the present example, the weight structure  780  protrudes from the external contour of the sole  718 , and is thus at least partially external to allow for greater adjustment of the head CG  770 . In some examples, the weight structure  780  can comprise a mass of approximately 2 grams to approximately 50 grams, and/or a volume of approximately 1 cc to approximately 30 cc. In other examples, the weight structure  780  can remain flush with the external contour of the body  702 . 
     In many embodiments, the removable weight  782  can comprise a mass of approximately 0.5 grams to approximately 30 grams, and can be replaced with one or more other similar removable weights to adjust the location of the head CG  770 . In the same or other examples, the weight center  786  can comprise at least one of a center of gravity of the removable weight  782 , and/or a geometric center of removable weight  782 . 
     iv. Embedded Weights 
     In some embodiments, the club head  700  can include one or more embedded weights to position the discretionary weight on the sole  718 , in the skirt  728 , and/or near the back end  710  of the club head  700  to achieve a low and back head CG position. The one or more embedded weights of club head  700  can be similar or identical to the one or more embedded weights  383  of club head  300 , or the one or more embedded weights of club head  500 . In many embodiments, the one or more embedded weights are permanently fixed to or within the club head  700 . In these embodiments, the embedded weight can be similar to the high density metal piece (HDMP) described in U.S. Provisional Patent Appl. No. 62/372,870, entitled “Embedded High Density Casting.” 
     In many embodiments, the one or more embedded weights are positioned near the back end  710  of the club head. For example, a weight center of the embedded weight can be 2005 and 8 o&#39;clock ray  2008  of the clock grid. In many embodiments, the one or more embedded weights can be positioned on the skirt  728  and near the back end  710  of the club head  700 , on the sole  718  and near the back end  710  of the club head  700 , or on the skirt  728  and the sole  718  near the back end  710  of the club head  700 . 
     In many embodiments, the weight center of the one or more embedded weights is positioned within 0.10 inches, within 0.20 inches, within 0.30 inches, within 0.40 inches, within 0.50 inches, within 0.60 inches, within 0.70 inches, within 0.80 inches, within 0.90 inches, within 1.0 inches, within 1.1 inches, within 1.2 inches, within 1.3 inches, within 1.4 inches, or within 1.5 inches of a perimeter of the club head  700  when viewed from a top view or bottom view ( FIG. 17 ). In these embodiments, the proximity of the embedded weight to the perimeter of the club head  700  can maximize the low and back head CG position, the crown-to-sole moment of inertia I xx , and/or the heel-to-toe moment of inertia I yy . 
     In many embodiments, the weight center of the one or more embedded weights is positioned at a distance from the head CG  770  greater than 1.6 inches, greater than 1.7 inches, greater than 1.8 inches, greater than 1.9 inches, greater than 2.0 inches, greater than 2.1 inches, greater than 2.2 inches, greater than 2.3 inches, greater than 2.4 inches, greater than 2.5 inches, greater than 2.6 inches, greater than 2.7 inches, greater than 2.8 inches, greater than 2.9 inches, or greater than 3.0 inches. 
     In many embodiments, the weight center of the one or more embedded weights is positioned at a distance from the geometric center  740  of the strikeface  704  greater than 4.0 inches, greater than 4.1 inches, greater than 4.2 inches, greater than 4.3 inches, greater than 4.4 inches, greater than 4.5 inches, greater than 4.6 inches, greater than 4.7 inches, greater than 4.8 inches, greater than 4.9 inches, or greater than 5.0 inches. 
     In many embodiments, the one or more embedded weights can comprise a mass between 3.0-90 grams. For example, in some embodiments, the one or more embedded weights can comprise a mass between 3.0-25 grams, between 10-40 grams, between 20-50 grams, between 30-60 grams, between 40-70 grams, between 50-80 grams, or between 60-90 grams. In embodiments where the one or more embedded weights include more than one weight, each of the embedded weights can comprise the same or a different mass. 
     In many embodiments, the one or more embedded weights can comprise a material having a specific gravity between 10.0-22.0. For example, in many embodiments, the one or more embedded weights can comprise a material having a specific gravity greater than 10.0, greater than 11.0, greater than 12.0, greater than 13.0, greater than 14.0, greater than 15.0, greater than 16.0, greater than 17.0, greater than 18.0, or greater than 19.0. In embodiments where the one or more embedded weights include more than one weight, each of the embedded weights can comprise the same or a different material. 
     v. Steep Crown Angle 
     In some embodiments as illustrated in  FIGS. 18-20 , the golf club head  700  can further include a steep crown angle  788  to achieve the low and back head CG position. The steep crown angle  788  positions the back end of the crown  716  toward the sole  718  or ground, thereby lowering the club head CG position. 
     The crown angle  788  is measured as the acute angle between a crown axis  1090  and the front plane  1020 . In these embodiments, the crown axis  1090  is located in a cross-section of the club head  700  taken along a plane positioned perpendicular to the ground plane  1030  and the front plane  1020 . The crown axis  1090  can be further described with reference to a top transition boundary and a rear transition boundary. 
     The club head  700  includes a top transition boundary extending between the front end  708  and the crown  716  from near the heel  720  to near the toe  722 . The top transition boundary includes a crown transition profile  790  when viewed from a side cross sectional view taken along a plane perpendicular to the front plane  1020  and perpendicular to the ground plane  1030  when the club head  700  is at an address position. The side cross sectional view can be taken along any point of the club head  700  from near the heel  720  to near the toe  722 . The crown transition profile  790  defines a front radius of curvature  792  extending from the front end  708  of the club head  700  where the contour departs from the roll radius and/or the bulge radius of the strikeface  704  to a crown transition point  794  indicating a change in curvature from the front radius of curvature  792  to the curvature of the crown  716 . In some embodiments, the front radius of curvature  792  comprises a single radius of curvature extending from the top end  793  of the strikeface perimeter  742  near the crown  716  where the contour departs from the roll radius and/or the bulge radius of the strikeface  704  to a crown transition point  794  indicating a change in curvature from the front radius of curvature  792  to one or more curvatures of the crown  716 . 
     The club head  700  further includes a rear transition boundary extending between the crown  716  and the skirt  728  from near the heel  720  to near the toe  722 . The rear transition boundary includes a rear transition profile  796  when viewed from a side cross sectional view taken along a plane perpendicular to the front plane  1020  and perpendicular to the ground plane  1030  when the club head  700  is at an address position. The cross sectional view can be taken along any point of the club head  700  from near the heel  720  to near the toe  722 . The rear transition profile  796  defines a rear radius of curvature  798  extending from the crown  716  to the skirt  728  of the club head  700  along the rear transition boundary. In many embodiments, the rear radius of curvature  798  comprises a single radius of curvature that transitions the crown  716  to the skirt  728  of the club head  700 . A first rear transition point  802  is located at the junction between the crown  716  and the rear transition boundary. A second rear transition point  803  is located at the junction between the rear transition boundary and the skirt  728  of the club head  700 . 
     The front radius of curvature  792  of the top transition boundary can remain constant, or can vary from near the heel  520  to near the toe  522  of the club head  700 . Similarly, the rear radius of curvature  798  of the rear transition boundary can remain constant, or can vary from near the heel  720  to near the toe  722  of the club head  700 . 
     The crown axis  1090  extends between the crown transition point  794  near the front end  708  of the club head  700  and the rear transition point  802  near the back end  710  of the club head  700 . The crown angle  788  can remain constant, or can vary from near the heel  720  to near the toe  522  of the club head  700 . For example, the crown angle  788  can vary when the side cross sectional view is taken at different locations relative to the heel  720  and the toe  722 . 
     In many embodiments, the maximum crown angle  788  taken at any location from near the toe  722  to near the heel  720  is less than 79 degrees, less than approximately 95 degrees, less than approximately 93 degrees, less than approximately 91 degrees, less than approximately 89 degrees, less than approximately 87 degrees, less than approximately 85 degrees, less than approximately 83 degrees, less than approximately 81 degrees, less than approximately 79 degrees, less than approximately 77 degrees, or less than approximately 75 degrees. For example, in some embodiments, the maximum crown angle is between 65 degrees and 95 degrees, between 65 degrees and 90 degrees, or between 65 degrees and 85 degrees. 
     In many embodiments, reducing the crown angle  788  compared to current club heads generates a steeper crown or a crown positioned closer to the ground plane  1030  when the club head  700  is at an address position. Accordingly, the reduced crown angle  788  can result in a lower head CG position compared to a club head with a higher crown angle. 
     vi. Hosel Sleeve Weight 
     In some embodiments, the head CG height  774  and/or head CG depth  772  can be achieved by reducing the mass of the hosel sleeve  734 . Removing excess weight from the hosel sleeve  734  results in increased discretionary weight that can be strategically repositioned to regions of the club head  700  to achieve the desired low and back club head CG position. 
     Reducing the mass of the hosel sleeve  734  can be achieved by thinning the sleeve walls, reducing the height of the hosel sleeve  734 , reducing the diameter of the hosel sleeve  734 , and/or by introducing voids in the walls of the hosel sleeve  734 . In many embodiments, the mass of the hosel sleeve  734  can be less than 6 grams, less than 5.5 grams, less than 5.0 grams, less than 4.5 grams, or less than 4.0 grams. In many embodiments, the club head  700  having the reduced mass hosel sleeve can result in a lower (close to the sole) and farther back (closer to the back end) club head CG position than a similar club head with a heavier hosel sleeve. 
     B. Aerodynamic Drag 
     In many embodiments, the club head  700  comprises a low and back club head CG position and an increased club head moment of inertia, in combination with reduced aerodynamic drag. 
     In many embodiments, the club head  700  experiences an aerodynamic drag force less than approximately 1.25 lbf, less than 1.0 lbf, less than 0.95 lbf, less than 0.90 lbf, less than 0.85 lbf, less than 0.83 lbf, or less than 0.80 lbf when tested in a wind tunnel with a squared face and an air speed of 98 miles per hour (mph). In these or other embodiments, the club head  700  experiences an aerodynamic drag force less than approximately 1.25 lbf, less than 1.0 lbf, less than 0.95 lbf, less than 0.90 lbf, less than 0.85 lbf, less than 0.83 lbf, or less than 0.80 lbf when simulated using computational fluid dynamics with a squared face and an air speed of 98 miles per hour (mph). In these embodiments, the airflow experienced by the club head  700  having the squared face is directed at the strikeface  704  in a direction perpendicular to the X′Y′ plane. The club head  700  having reduced aerodynamic drag can be achieved using various means, as described below. 
     i. Crown Angle Height 
     In some embodiments, reducing the crown angle  788  to form a steeper crown and lower head CG position may result in an undesired increase in aerodynamic drag due to increased air flow separation over the crown during a swing. To prevent increased drag associated with a reduced crown angle  788 , a maximum crown height  804  can be increased. Referring to  FIG. 18 , the maximum crown height  804  is the greatest distance between the surface of the crown  716  and the crown axis  1090  taken at any side cross sectional view of the club head  700  along a plane positioned parallel to the Y′Z′ plane. In many embodiments, a greater maximum crown height  804  results in the crown  716  having a greater curvature. A greater curvature in the crown  716  moves the location of the air flow separation during a swing further back on the club head  700 . In other words, a greater curvature allows the airflow to stay attached to club head  700  for a longer distance along the crown  716  during a swing. Moving the airflow separation point back on the crown  716  can result in reduced aerodynamic drag and increased club head swing speeds, thereby resulting in increased ball speed and distance. 
     In many embodiments, the maximum crown height  804  can be greater than approximately 0.10 inch (2.5 mm), greater than approximately 0.20 inch (5 mm), greater than approximately 0.30 inch (7.5 mm), or greater than approximately 0.40 inch (10 mm). Further, in other embodiments, the maximum crown height  804  can be within the range of 0.10 inch (2.5 mm) to 0.40 inch (10 mm), or 0.10 inch (2.5 mm) to 0.60 inch (15 mm), or 0.20 inch (5 mm) to 0.60 inch (15 mm). For example, in some embodiments, the maximum crown height  804  can be approximately 0.20 inch (5 mm), approximately 0.24 inch (6 mm), approximately 0.28 inch (7 mm), approximately 0.31 inch (8 mm), or approximately 0.35 inch (9 mm). 
     ii. Transition Profiles 
     In many embodiments, the transition profiles of the club head  700  from the strikeface  704  to the crown  716 , the strikeface  704  to the sole  718 , and/or the crown  716  to the sole  718  along the back end  710  of the club head  700  can affect the aerodynamic drag on the club head  700  during a swing. 
     In some embodiments, the club head  700  having the top transition boundary defining the crown transition profile  790 , and the rear transition boundary defining the rear transition profile  796  further includes a sole transition boundary defining a sole transition profile  810 . The sole transition boundary extends between the front end  708  and the sole  718  from near the heel  720  to near the toe  720 . The sole transition boundary includes a sole transition profile  810  when viewed from a side cross sectional view taken along a plane parallel to the Y′Z′ plane. The side cross sectional view can be taken along any point of the club head  700  from near the heel  720  to near the toe  710 . The sole transition profile  810  defines a sole radius of curvature  812  extending from the front end  708  of the club head  700  where the contour departs from the roll radius and/or the bulge radius of the strikeface  704  to a sole transition point  814  indicating a change in curvature from sole radius of curvature  812  to the curvature of the sole  718 . In some embodiments, the sole radius of curvature  812  comprises a single radius of curvature extending from the bottom end  813  of the strikeface perimeter  742  near the sole  818  where the contour departs from the roll radius and/or the bulge radius of the strikeface  704  to a sole transition point  814  indicating a change in curvature from the sole radius of curvature  812  to a curvature of the sole  814 . 
     In many embodiments, the crown transition profile  790 , the sole transition profile  810 , and the rear transition profile  796  can be similar to the crown transition, sole transition, and rear transition profiles described in U.S. patent Ser. No. 15/233,486, entitled “Golf Club Head with Transition Profiles to Reduce Aerodynamic Drag.” Further, the front radius of curvature  792  can be similar to the first crown radius of curvature, the sole radius of curvature  812  can be similar to the first sole radius of curvature, and the rear radius of curvature  798  can be similar to the rear radius of curvature described U.S. patent Ser. No. 15/233,486, entitled “Golf Club Head with Transition Profiles to Reduce Aerodynamic Drag.” 
     In some embodiments, the front radius of curvature  792  can range from approximately 0.10 to 0.50 inches (0.25 to 1.27 cm). Further, in other embodiments, the front radius of curvature  792  can be less than 0.40 inches (1.02 cm), less than 0.375 inches (0.95 cm), less than 0.35 inches (0.89 cm), less than 0.325 inches (0.83 cm), or less than 0.30 inches 0.76 cm). For example, the front radius of curvature  792  can be approximately 0.18 inches (0.46 cm), 0.20 inches (0.51 cm), 0.22 inches (0.66 cm), 0.24 inches (0.61 cm), 0.26 inches (0.66 cm), 0.28 inches (0.71 cm), or 0.30 inches (0.76 cm). 
     In some embodiments, the sole radius of curvature  812  can range from approximately 0.05 to 0.25 inches (0.13 to 0.64 cm). For example, the sole radius of curvature  812  can be less than approximately 0.3 inches (0.76 cm), less than approximately 0.275 inches (0.70 cm), less than approximately 0.25 inches (0.64 cm), less than approximately 0.2 inches (0.51 cm), less than approximately 0.15 inches (0.38 cm), or less than approximately 0.1 inches (0.25 cm). For further example, the sole radius of curvature  812  can be approximately 0.10 inches (0.25 cm), 0.15 inches (0.38 cm), 0.20 inches (0.51 cm), or 0.25 inches (0.64 cm). 
     In some embodiments, the rear radius of curvature  798  can range from approximately 0.10 to 0.25 inches (0.25 to 0.64 cm). For example, the rear radius of curvature  798  can be less than approximately 0.3 inches (0.76 cm), less than approximately 0.275 inches (0.70 cm), less than approximately 0.25 inches (0.64 cm), less than approximately 0.225 inches (0.57 cm), or less than approximately 0.20 inches (0.51 cm). For further example, the rear radius of curvature  798  can be approximately 0.10 inches (0.25 cm), 0.15 inches (0.38 cm), 0.20 inches (0.51 cm), or 0.25 inches (0.64 cm). 
     iii. Turbulators 
     In some embodiments as illustrated in  FIG. 21 , the club head  700  can further include a plurality of turbulators  818 , as described in U.S. patent application Ser. No. 13/536,753, now U.S. Pat. No. 8,608,587, granted on Dec. 17, 2013, entitled “Golf Club Heads with Turbulators and Methods to Manufacture Golf Club Heads with Turbulators,” which is incorporated fully herein by reference. In many embodiments, the plurality of turbulators  814  disrupt the airflow thereby creating small vortices or turbulence inside the boundary layer to energize the boundary layer and delay separation of the airflow on the crown during a swing. 
     In some embodiments, the plurality of turbulators  614  can be adjacent to the crown transition point  994  of the club head  700 . The plurality of turbulators  814  project from an outer surface of the crown  716  and include a length extending between the front end  708  and the back end  710  of the club head  700 , and a width extending from the heel  720  to the toe  722  of the club head  722 . In many embodiments, the length of the plurality of turbulators  814  is greater than the width. In some embodiments, the plurality of turbulators  814  can comprise the same width. In some embodiments, the plurality of turbulators  814  can vary in height profile. In some embodiments, the plurality of turbulators  814  can be higher toward the apex of the crown  716  than in comparison to the front of the crown  716 . In other embodiments, the plurality of turbulators  814  can be higher toward the front of the crown  716 , and lower in height toward the apex of the crown  716 . In other embodiments, the plurality of turbulators  814  can comprise a constant height profile. Further, in many embodiments, at least a portion of at least one turbulator is located between the strikeface and an apex of the crown, and the spacing between adjacent turbulators is greater than the width of each of the adjacent turbulators. 
     iv. Back Cavity 
     In some embodiments as illustrated in  FIGS. 20 and 22 , the club head  700  can further include a cavity  820  located at the back end  710  and in the trailing edge  728  of the club head  700 . In many embodiments, the cavity  820  can be similar to cavity  420  on club head  300  or cavity  620  on club head  500 . Further, the cavity  820  can be similar to the cavity described in U.S. patent application Ser. No. 14/882,092, entitled “Golf Club Heads with Aerodynamic Features and Related Methods.” In many embodiments, the cavity  820  can break the vortices generated behind golf club head  700  into smaller vortices to reduce the size of the wake and/or reduce drag. In some embodiments, breaking the vortices into smaller vortices can generate a region of high pressure behind golf club head  700 . In some embodiments, this region of high pressure can push golf club head  700  forward, reduce drag, and/or enhance the aerodynamic design of golf club head  700 . In many embodiments, the net effect of smaller vortices and reduced drag is an increase in the speed of golf club head  700 . This effect can lead to higher speeds at which a golf ball leaves strikeface  704  after impact to increase ball travel distance. 
     In many embodiments, the cavity  820  can include a back wall  822  that is oriented in a direction perpendicular to the X′Z′ plane and can include a width measured in a direction from the heel  720  to the toe  722 , a depth  824 , and a height  826 . The width of the cavity  820  can be approximately 1.0 inches (approximately 2.54 centimeters (cm)) to approximately 8 inch (approximately 20.32 cm), approximately 1.0 inches (approximately 2.54 cm) to approximately 2.25 inches (approximately 5.72 cm), or approximately 1.75 inches (approximately 4.5 cm) to approximately 2.25 inches (approximately 5.72 cm). For example, the width of the cavity  820  can be approximately 2.0 inches (5.08 cm), 3.0 inches (7.62 cm), 4.0 inches (10.16 cm), 5.0 inches (12.7 cm), 6.0 inches (15.24 cm), or 7.0 inches (17.78 cm). In some embodiments, the width of the cavity  820  can remain constant from near the top of the cavity  820  (toward the crown  716  of the club head  700 ) to near the bottom of the cavity  820  (toward the sole  718  of the club head  700 ). In other embodiments, the width of the cavity  820  can vary from near the top to near the bottom. In the illustrated embodiment of  FIG. 22 , the width of the cavity  820  is largest near the top and smallest near the bottom. In other embodiments, the width of the cavity  820  can vary according to any profile. For example, in other embodiments, the width of the cavity  820  can be longest at the top, at the bottom, at the center, or at any other location extending from the top to the bottom of the cavity  820 . 
     The depth  824  of the cavity  820  can be approximately 0.025 inch (approximately 0.127 cm) to approximately 0.250 inch (approximately 0.635 cm), or approximately 0.025 inch (approximately 0.127 cm) to approximately 0.150 inch (approximately 0.381 cm). For example, the depth  824  of the cavity  820  can be approximately 0.1 inch (approximately 0.254 cm), or approximately 0.05 inch (approximately 0.127 cm). In some embodiments, the depth  824  of the cavity  820  can remain constant between the heel and the toe and/or between the top and the bottom of the cavity  820 . In other embodiments, the depth  824  of the cavity  820  can vary between the heel and the toe and/or between the top and the bottom of the cavity  820 . For example, the depth  824  of the cavity  820  can be the largest near the heel, near the toe, near the crown, near the sole, near the center, or at any combination of the described locations. 
     The height  826  of the cavity  820  can be measured in a direction from the crown  716  to the sole  718 . The height  826  of the cavity  820  can be approximately 0.19 inch (approximately 0.48 cm) to approximately 0.21 inch (approximately 0.53 cm). In some embodiments, the height  826  of the cavity  820  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.50 inch (approximately 1.27 cm). In some embodiments, the height  826  of the cavity  820  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.40 inch (approximately 1.02 cm). In some embodiments, the height  826  of the cavity  820  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.30 inch (approximately 0.76 cm). In some embodiments, the height  826  of the cavity  820  can be approximately 0.10 inch (approximately 0.25 cm) to approximately 0.20 inch (approximately 0.51 cm). In some embodiments, the height  826  of the cavity  820  can remain constant between the heel and the toe of the cavity  820 . In other embodiments, the height  826  of the cavity  820  can vary between the heel and the toe of the cavity  820 . For example, the height  826  of the cavity  820  can be the largest near the heel, near the toe, near the center, or at any combination of the described locations. 
     v. Hosel Structure 
     In some embodiments, the hosel structure  730  can have a smaller outer diameter to reduce the aerodynamic drag on the club head  700  during a swing, compared to a similar club head having a larger diameter hosel structure. In many embodiments, the hosel structure  730  has an outer diameter less than 0.545 inches. For example, the hosel structure  730  can have an outer diameter less than 0.60 inches, less than 0.59 inches, less than 0.58 inches, less than 0.57 inches, less than 0.56 inches, less than 0.55 inches, less than 0.54 inches, less than 0.53 inches, less than 0.52, less than 0.51 inches, or less than 0.50 inches. In many embodiments, the outer diameter of the hosel structure  730  is reduced while maintaining adjustability of the loft angle and/or lie angle of the club head  700 . 
     C. Balance of CG Position, Moment of Inertia, and Aerodynamic Drag 
     In current golf club head design, increasing or maximizing the moment of inertia of the club head can adversely affect other performance characteristics of the club head, such as aerodynamic drag. The club head  700  described herein increases or maximizes the club head moment of inertia, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  700  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     In the examples of club head  700  described below, the aerodynamic drag of the club head is measured using computational fluid dynamic simulations with the front end of the club head-oriented square into the airstream at an air speed of 102 miles per hour (mph). In other embodiments, the aerodynamic drag can be measured using other methods, such as using wind tunnel testing. 
     In many known golf club heads, increasing or maximizing the moment of inertia of the club head adversely affects aerodynamic drag.  FIGS. 23A-C  illustrate that for many known club heads having a volume and/or loft angle similar to club head  700 , as the club head moment of inertia increases (to increase club head forgiveness), the force of drag during a swing increases (thereby reducing swing speed and ball distance). 
     For example, referring to  FIG. 23A , for many known club heads, as the moment of inertia about the x-axis increases, the force of drag increases. For further example, referring to  FIG. 23B , for many known club heads, as the moment of inertia about the y-axis increases, the force of drag increases. For further example referring to  FIG. 23C , for many known club heads, as the combined moment of inertia (i.e. the sum of the moment of inertia about the x-axis and the moment of inertia about the y-axis) increases, the force of drag increases. 
     The club head  700  described herein increases or maximizes the club head moment of inertia compared to known club heads having similar volume and/or loft angle, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  700  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     In many embodiments, referring to  FIG. 24 , the club head  700  satisfies one or more of the following relations, such that the combined moment of inertia (I xx +I yy ) of the club head is increased, while maintaining or reducing the drag force (F D ) on the club head, compared to known golf club heads having similar volume and/or loft angle. 
     
       
         
           
             
               
                 
                   
                     
                       
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     For example, in many embodiments, the club head  700  satisfies Relation 9. In other embodiments, the club head  700  can satisfy Relation 9, and can have a combined moment of inertia greater than 490 g·cm 2 , greater than 5000 g·cm 2 , greater than 5100 g·cm 2 , greater than 5200 g·cm 2 , greater than 5300 g·cm 2 , greater than 5400 cm 2 , greater than 5500 g·cm 2 , greater than 5600 g·cm 2 , greater than 5700 g·cm 2 , greater than 5800 g·cm 2 , greater than 5900 g·cm 2 , or greater than 6000 g·cm 2 . In other embodiments still, the club head  700  can satisfy Relation 9, and can have a drag force less than 1.25 lbf, less than 1.0 lbf, less than 0.95 lbf, less than 0.90 lbf, less than 0.850 lbf, less than 0.83 lbf, or less than 0.80 lbf. 
     For further example, in many embodiments, the club head  700  satisfies Relation 10. In other embodiments, the club head  700  can satisfy Relation 10, and can have a combined moment of inertia greater than 4900 g·cm 2 , greater than 5000 g·cm 2 , greater than 5100 g·cm 2 , greater than 5200 g·cm 2 , greater than 5300 g·cm 2 , greater than 5400 cm 2 , greater than 5500 g·cm 2 , greater than 5600 g·cm 2 , greater than 5700 g·cm 2 , greater than 5800 g·cm 2 , greater than 5900 g·cm 2 , or greater than 6000 g·cm 2 . In other embodiments still, the club head  700  can satisfy Relation 10, and can have a drag force less than 1.25 lbf, less than 1.0 lbf, less than 0.95 lbf, less than 0.90 lbf, less than 0.850 lbf, less than 0.83 lbf, or less than 0.80 lbf. 
     i. CG Position and Aerodynamic Drag 
     In many known golf club heads, shifting the CG position farther back to increase launch angle of a golf ball and/or to increase club head inertia, can adversely affect other performance characteristics of the club head, such as aerodynamic drag.  FIG. 25  illustrates that for many known club heads having volume and/or loft angle similar to club head  700 , as the club head CG depth increases (to increase club head forgiveness and or launch angle), the force of drag during a swing increases (thereby reducing swing speed and ball distance). For example, referring to  FIG. 25 , for many known club heads, as the head CG depth increases, the force of drag on the club head increases. 
     The club head  700  described herein increases or maximizes the club head CG depth compared to known club heads having similar volume and/or loft angle, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  700  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     In many embodiments, referring to  FIG. 26 , the club head  700  satisfies one or more of the following relations, such that the head CG depth (CG D ) is increased, while maintaining or reducing the drag force (F D ) on the club head, compared to known golf club heads having a similar volume and/or loft angle. 
     
       
         
           
             
               
                 
                   
                     
                       
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     For example, in many embodiments, the club head  700  satisfies Relation 11. In other embodiments, the club head  700  can satisfy Relation 11, and can have a head CG depth greater than 1.1 inches, greater than 1.2 inches, greater than 1.3 inches, greater than 1.4 inches, greater than 1.5 inches, greater than 1.6 inches, greater than 1.7 inches, or greater than 1.8 inches. Further, in other embodiments, the club head  700  can satisfy Relation 11, and can have a drag force less than 1.25 lbf, less than 1.0 lbf, less than 0.95 lbf, less than 0.90 lbf, less than 0.85 lbf, less than 0.83 lbf, or less than 0.80 lbf. 
     For further example, in many embodiments, the club head  700  satisfies Relation 12. In other embodiments, the club head  700  can satisfy Relation 7, and can have a head CG depth greater than 1.1 inches, greater than 1.2 inches, greater than 1.3 inches, greater than 1.4 inches, greater than 1.5 inches, greater than 1.6 inches, greater than 1.7 inches, or greater than 1.8 inches. Further, in other embodiments, the club head  700  can satisfy Relation 12, and can have a drag force less than 1.25 lbf, less than 1.0 lbf, less than 0.95 lbf, less than 0.90 lbf, less than 0.85 lbf, less than 0.83 lbf, or less than 0.80 lbf. For further example, in many embodiments, the club head  300 ,  500  satisfies Relation 7, and has a drag force less than 1.16 lbf. 
     ii. Moment of Inertia and CG Depth 
     Referring to  FIG. 27 , the combined moment of inertia and/or head CG depth of many known golf club heads are limited. For example, many known golf club heads having a volume and/or loft angle similar to club head  700  have a head CG depth less than 1.2 inches and a combined moment of inertia less than 5000 g·cm 2 . The club head  700  described herein has a greater head CG depth and a greater combined moment of inertia than known club heads having similar volume and/or loft angle, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  300 ,  500  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     For example, in many embodiments the club head  700  has a head CG depth greater than 1.22 inches and a combined moment of inertia greater than 5000 g·cm 2 . In other embodiments, the club head  300 ,  500  can have a head CG depth greater than 1.1 inches, greater than 1.2 inches, greater than 1.3 inches, greater than 1.4 inches, greater than 1.5 inches, greater than 1.6 inches, greater than 1.7 inches, or greater than 1.8 inches. Further, in other embodiments, the club head  700  can have a combined moment of inertia greater than 5000 g·cm 2 , greater than 5100 g·cm 2 , greater than 5200 g·cm 2 , greater than 5300 g·cm 2 , greater than 5400 ·cm 2 , greater than 5500 g·cm 2 , greater than 5600 g·cm 2 , greater than 5700 g·cm 2 , greater than 5800 g·cm 2 , greater than 5900 g·cm 2 , or greater than 6000 g·cm 2 . 
     IV. Hybrid-Type Club Head 
     According to another embodiment, a golf club head  900  can comprise a hybrid-type club head. In many embodiments, club head  900  comprises the same or similar parameters as club head  100 , wherein the parameters are described with the club head  100  reference numbers plus  800 . 
     In many embodiments, the loft angle of the club head  900  is less than approximately 40 degrees, less than approximately 39 degrees, less than approximately 38 degrees, less than approximately 37 degrees, less than approximately 36 degrees, less than approximately 35 degrees, less than approximately 34 degrees, less than approximately 33 degrees, less than approximately 32 degrees, less than approximately 31 degrees, or less than approximately 30 degrees. Further, in many embodiments, the loft angle of the club head  900  is greater than approximately 16 degrees, greater than approximately 17 degrees, greater than approximately 18 degrees, greater than approximately 19 degrees, greater than approximately 20 degrees, greater than approximately 21 degrees, greater than approximately 22 degrees, greater than approximately 23 degrees, greater than approximately 24 degrees, or greater than approximately 25 degrees. 
     In many embodiments, the volume of the club head  900  is less than approximately 200 cc, less than approximately 175 cc, less than approximately 150 cc, less than approximately 125 cc, less than approximately 100 cc, or less than approximately 75 cc. In some embodiments, the volume of the club head can be approximately 100 cc-150 cc, approximately 75 cc-150 cc, approximately 100 cc-125 cc, approximately 75 cc-100 cc, or approximately 75 cc-125 cc. In other embodiments, the golf club head  900  can comprise any type of golf club head having a loft angle and volume as described herein. 
     In many embodiments, the length  962  of the club head  900  is between 3.5 inches and 4.5 inches, between 3.75 inches and 4.75 inches, or between 3.5 inches and 4.75 inches. In other embodiments, the length  962  of the club head  900  is less than 4.5 inches, less than 4.4 inches, greater than 4.3 inches, less than 4.2 inches, less than 4.1 inches, or less than 4.0 inches. 
     In many embodiments, the depth  960  of the club head  900  is at least 0.70 inches less than the length  962  of the club head  900 . In many embodiments, the depth  960  of the club head  900  is between 2.0 inches and 3.0 inches, between 2.0 inches and 2.75 inches, or between 2.0 inches and 2.5 inches. In other embodiments, the depth  960  of the club head  900  is less than 3.0 inches, less than 2.9 inches, less than 2.8 inches, less than 2.7 inches, less than 2.6 inches, less than 2.5 inches, less than 2.4 inches, less than 2.3 inches, less than 2.2 inches, less than 2.1 inches, or less than 2.0 inches. 
     In many embodiments, the height  964  of the club head  900  is less than approximately 1.75 inches. In other embodiments, the height  964  of the club head  900  is less than 2.0 inches, less than 1.9 inches, less than 1.8 inches, less than 1.7 inches, less than 1.6 inches, or less than 1.5 inches. For example, in some embodiments, the height of the club head  900  can be between 1.5-1.75 inches, between 1.0-1.75 inches, between 1.5-2.0 inches, or between 1.25-1.75 inches. 
     The club head  900  further comprises a balance of various additional parameters, such as head CG position, club head moment of inertia, and aerodynamic drag, to provide both improved impact performance characteristics (e.g. spin, launch angle, speed, forgiveness) and swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact). In many embodiments, the balance of parameters described below provides improved impact performance while maintaining or improving swing performance characteristics. Further, in many embodiments, the balance of parameters described below provides improved swing performance characteristics while maintaining or improving impact performance characteristics. 
     A. Center of Gravity Position and Moment of Inertia 
     In many embodiments, a low and back club head CG and increased moment of inertia can be achieved by increasing discretionary weight and repositioning discretionary weight in regions of the club head having maximized distances from the head CG. Increasing discretionary weight can be achieved by thinning the crown and/or using optimized materials, as described above relative to the head CG position. Repositioning discretionary weight to maximize the distance from the head CG can be achieved using removable weights, embedded weights, or a steep crown angle, as described above relative to the head CG position. 
     In many embodiments, the club head  900  comprises a crown-to-sole moment of inertia I xx  greater than approximately 3000 g·cm 2 , greater than approximately 3250 g·cm 2 , greater than approximately 3500 g·cm 2 , greater than approximately 3750 g·cm 2 , greater than approximately 4000 g·cm 2 , greater than approximately 4250 g·cm 2 , greater than approximately 4500 g·cm 2 , greater than approximately 4750 g·cm 2 , greater than approximately 5000 g·cm 2 , greater than approximately 5250 g·cm 2 , greater than approximately 5500 g·cm 2 , greater than approximately 5750 g·cm 2 , greater than approximately 6000 g·cm 2 , greater than approximately 6250 g·cm 2 , greater than approximately 6500 g·cm 2 , greater than approximately 6750 g·cm 2 , or greater than approximately 7000 g·cm 2 . 
     In many embodiments, the club head  900  comprises a heel-to-toe moment of inertia I yy  greater than approximately 5000 g·cm 2 , greater than approximately 5250 g·cm 2 , greater than approximately 5500 g·cm 2 , greater than approximately 5750 g·cm 2 , greater than approximately 6000 g·cm 2 , greater than approximately 6250 g·cm 2 , greater than approximately 6500 g·cm 2 , greater than approximately 6750 g·cm 2 , or greater than approximately 7000 g·cm 2 . 
     In many embodiments, the club head  900  comprises a combined moment of inertia (i.e. the sum of the crown-to-sole moment of inertia I xx  and the heel-to-toe moment of inertia I yy ) greater than 8000 g·cm 2 , greater than 8500 g·cm 2 , greater than 8750 g·cm 2 , greater than 9000 g·cm 2 , greater than 9250 g·cm 2 , greater than 9500 g·cm 2 , greater than 9750 g·cm 2 , greater than 10000 g·cm 2 , greater than 10250 g·cm 2 , greater than 10500 g·cm 2 , greater than 10750 g·cm 2 , greater than 11000 g·cm 2 , greater than 11250 g·cm 2 , greater than 11500 g·cm 2 , greater than 11750 g·cm 2 , or greater than 12000 g·cm 2 . 
     In many embodiments, the club head  900  comprises a head CG height  974  less than approximately 0.20 inches, less than approximately 0.15 inches, less than approximately 0.10 inches, less than approximately 0.09 inches, less than approximately 0.08 inches, less than approximately 0.07 inches, less than approximately 0.06 inches, or less than approximately 0.05 inches. Further, in many embodiments, the club head  900  comprises a head CG height  974  having an absolute value less than approximately 0.20 inches, less than approximately 0.15 inches, less than approximately 0.10 inches, less than approximately 0.09 inches, less than approximately 0.08 inches, less than approximately 0.07 inches, less than approximately 0.06 inches, or less than approximately 0.05 inches. 
     Further, in many embodiments, the club head  900  comprises a head CG depth  972  greater than approximately 0.75 inches, greater than approximately 0.80 inches, greater than approximately 0.85 inches, greater than approximately 0.90 inches, greater than approximately 0.95 inches, or greater than approximately 1.0 inches. 
     The club head  900  having the reduced head CG height  974  can reduce the backspin of a golf ball on impact compared to a similar club head having a higher head CG height. In many embodiments, reduced backspin can increase both ball speed and travel distance for improve club head performance. Further, the club head  900  having the increased head CG depth  972  can increase the heel-to-toe moment of inertia compared to a similar club head having a head CG depth closer to the strikeface. Increasing the heel-to-toe moment of inertia can increase club head forgiveness on impact to improve club head performance. Further still, the club head  900  having the increased head CG depth  973  can increase launch angle of a golf ball on impact by increasing the dynamic loft of the club head at delivery, compared to a similar club head having a head CG depth closer to the strikeface. 
     The head CG height  974  and/or head CG depth  972  can be achieved by reducing weight of the club head in various regions, thereby increasing discretionary weight, and repositioning discretionary weight in strategic regions of the club head  900  to shift the head CG lower and farther back. Various means to reduce and reposition club head weight are described below. 
     i. Thin Regions 
     In some embodiments, the head CG height  974  and/or head CG depth  972  can be achieved by thinning various regions of the club head to remove excess weight. Removing excess weight results in increased discretionary weight that can be strategically repositioned to regions of the club head  900  to achieve the desired low and back club head CG position. 
     In many embodiments, the club head  900  can have one or more thin regions. The one or more thin regions can be similar or identical to the one or more thin regions  376  of club head  300 , or the one or more thin regions of club heads  500 ,  700 . The one or more thin regions can be positioned on the strikeface  904 , the body  902 , or a combination of the strikeface  904  and the body  902 . Further, the one or more thin regions can be positioned on any region of the body  902 , including the crown  916 , the sole  918 , the heel  920 , the toe  922 , the front end  908 , the back end  910 , the skirt  928 , or any combination of the described positions. For example, in some embodiments, the one or more thin regions can be positioned on the crown  916 . For further example, the one or more thin regions can be positioned on a combination of the strikeface  904  and the crown  916 . For further example, the one or more thin regions can be positioned on a combination of the strikeface  904 , the crown  916 , and the sole  918 . For further example, the entire body  902  and/or the entire strikeface  904  can comprise a thin region. 
     In embodiments where one or more thin regions are positioned on the strikeface  904 , the thickness of the strikeface  904  can vary defining a maximum strikeface thickness and a minimum strikeface thickness. In these embodiments, the minimum strikeface thickness can be less than 0.10 inches, less than 0.09 inches, less than 0.08 inches, less than 0.07 inches, less than 0.06 inches, less than 0.05 inches, less than 0.04 inches, less than 0.03 inches, or less than 0.02 inches. In these or other embodiments, the maximum strikeface thickness can be less than 0.20 inches, less than 0.19 inches, less than 0.18 inches, less than 0.17 inches, less than 0.16 inches, less than 0.15 inches, less than 0.14 inches, less than 0.13 inches, less than 0.12 inches, less than 0.11 inches, or less than 0.10 inches. 
     In embodiments where one or more thin regions are positioned on the body  902 , the thin regions can comprise a thickness less than approximately 0.022 inches. In other embodiments, the thin regions comprise a thickness less than 0.025 inches, less than 0.020 inches, less than 0.019 inches, less than 0.018 inches, less than 0.017 inches, less than 0.016 inches, less than 0.015 inches, less than 0.014 inches, less than 0.013 inches, less than 0.012 inches, or less than 0.010 inches. For example, the thin regions can comprise a thickness between approximately 0.010-0.025 inches, between approximately 0.013-0.022 inches, between approximately 0.014-0.020 inches, between approximately 0.015-0.020 inches, between approximately 0.016-0.020 inches, between approximately 0.017-0.020 inches, or between approximately 0.018-0.020 inches. 
     In the illustrated embodiment, the thin regions vary in shape and position and cover approximately 25% of the surface area of club head  900 . In other embodiments, the thin regions can cover approximately 20-30%, approximately 15-35%, approximately 15-25%, approximately 10-25%, approximately 15-30%, or approximately 20-50% of the surface area of club head  900 . Further, in other embodiments, the thin regions can cover up to 5%, up to 10%, up to 15%, up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, or up to 50% of the surface area of club head  900 . 
     In many embodiments, the crown  916  comprises one or more thin regions, such that approximately 51% of the surface area of the crown  916  comprises thin regions. In other embodiments, the crown  916  comprises one or more thin regions, such that up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, up to 50%, up to 55%, up to 60%, up to 65%, up to 70%, or up to 75% of the crown  916  comprises thin regions. For example, in some embodiments, approximately 40-60% of the crown  916  can comprise thin regions. For further example, in other embodiments, approximately 35-65%, approximately 30-70%, or approximately 25-75% of the crown  916  can comprise thin regions. In some embodiments, the crown  916  can comprise one or more thin regions, wherein each of the one or more thin regions become thinner in a gradient fashion. In this exemplary embodiment, the one or more thin regions of the crown  916  extend in a heel-to-toe direction, and each of the one or more thin regions decrease in thickness in a direction from the strikeface  904  toward the back end  910 . 
     In many embodiments, the sole  918  comprises one or more thin regions, such that approximately 64% of the surface area of the sole  918  comprises thin regions. In other embodiments, the sole  918  comprises one or more thin regions, such that up to 20%, up to 25%, up to 30%, up to 35%, up to 40%, up to 45%, up to 50%, up to 55%, up to 60%, up to 65%, up to 70%, or up to 75% of the sole  918  comprises thin regions. For example, in some embodiments, approximately 40-60% of the sole  918  can comprise thin regions. For further example, in other embodiments, approximately 35-65%, approximately 30-70%, or approximately 25-75% of the sole  918  can comprise thin regions. 
     The thinned regions can comprise any shape, such as circular, triangular, square, rectangular, ovular, or any other polygon or shape with at least one curved surface. Further, on or more thinned regions can comprise the same shape as or a different shape than the remaining thinned regions. 
     In many embodiments, club head  900  having thin regions can be manufacturing using centrifugal casting. In these embodiments, centrifugal casting allows the club head  900  to have thinner walls than a club head manufactured using conventional casting. In other embodiments, portions of the club head  900  having thin regions can be manufactured using other suitable methods, such as stamping, forging, or machining. In embodiments where portions of the club head  900  having thin regions are manufactured using stamping, forging, or machining, the portions of the club head  900  can be coupled using epoxy, tape, welding, mechanical fasteners, or other suitable methods. 
     ii. Optimized Materials 
     In some embodiments, the strikeface  904  and/or the body  902  can comprise an optimized material having increased specific strength and/or increased specific flexibility. The specific flexibility is measured as a ratio of the yield strength to the elastic modulus of the optimized material. Increasing specific strength and/or specific flexibility can allow portions of the club head to be thinned, while maintaining durability. 
     In some embodiments, the first material of the strikeface  904  can be an optimized material, as described in U.S. Provisional Patent Appl. No. 62/399,929, entitled “Golf Club Heads with Optimized Material Properties.” In these or other embodiments, the first material comprising an optimized titanium alloy can have a specific strength greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 910,000 PSI/lb/in 3  (227 MPa/g/cm 3 ), greater than or equal to approximately 920,000 PSI/lb/in 3  (229 MPa/g/cm 3 ), greater than or equal to approximately 930,000 PSI/lb/in 3  (232 MPa/g/cm 3 ), greater than or equal to approximately 940,000 PSI/lb/in 3  (234 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 960,000 PSI/lb/in 3  (239 MPa/g/cm 3 ), greater than or equal to approximately 970,000 PSI/lb/in 3  (242 MPa/g/cm 3 ), greater than or equal to approximately 980,000 PSI/lb/in 3  (244 MPa/g/cm 3 ), greater than or equal to approximately 990,000 PSI/lb/in 3  (247 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), greater than or equal to approximately 1,100,000 PSI/lb/in 3  (274 MPa/g/cm 3 ), or greater than or equal to approximately 1,150,000 PSI/lb/in 3  (286 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the first material comprising an optimized titanium alloy can have a specific flexibility greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0091, greater than or equal to approximately 0.0092, greater than or equal to approximately 0.0093, greater than or equal to approximately 0.0094, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0096, greater than or equal to approximately 0.0097, greater than or equal to approximately 0.0098, greater than or equal to approximately 0.0099, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, or greater than or equal to approximately 0.0120. 
     In these or other embodiments, the first material comprising an optimized steel alloy can have a specific strength greater than or equal to approximately 650,000 PSI/lb/in 3  (162 MPa/g/cm 3 ), greater than or equal to approximately 700,000 PSI/lb/in 3  (174 MPa/g/cm 3 ), greater than or equal to approximately 750,000 PSI/lb/in 3  (187 MPa/g/cm 3 ), greater than or equal to approximately 800,000 PSI/lb/in 3  (199 MPa/g/cm 3 ), greater than or equal to approximately 810,000 PSI/lb/in 3  (202 MPa/g/cm 3 ), greater than or equal to approximately 820,000 PSI/lb/in 3  (204 MPa/g/cm 3 ), greater than or equal to approximately 830,000 PSI/lb/in 3  (207 MPa/g/cm 3 ), greater than or equal to approximately 840,000 PSI/lb/in 3  (209 MPa/g/cm 3 ), greater than or equal to approximately 850,000 PSI/lb/in 3  (212 MPa/g/cm 3 ), greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), greater than or equal to approximately 1,100,000 PSI/lb/in 3  (274 MPa/g/cm 3 ), greater than or equal to approximately 1,115,000 PSI/lb/in 3  (278 MPa/g/cm 3 ), or greater than or equal to approximately 1,120,000 PSI/lb/in 3  (279 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the first material comprising an optimized steel alloy can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0065, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, greater than or equal to approximately 0.0120, greater than or equal to approximately 0.0125, greater than or equal to approximately 0.0130, greater than or equal to approximately 0.0135, greater than or equal to approximately 0.0140, greater than or equal to approximately 0.0145, or greater than or equal to approximately 0.0150. 
     In these embodiments, the increased specific strength and/or increased specific flexibility of the optimized first material allow the strikeface  904 , or portions thereof, to be thinned, as described above, while maintaining durability. Thinning of the strikeface  904  can reduce the weight of the strikeface  904 , thereby increasing discretionary weight to be strategically positioned in other areas of the club head  900  to position the head CG low and back and/or increase the club head moment of inertia. 
     In some embodiments, the second material of the body  902  can be an optimized material, as described in U.S. Provisional Patent Appl. No. 62/399,929, entitled “Golf Club Heads with Optimized Material Properties.” In these or other embodiments, the second material comprising an optimized titanium alloy can have a specific strength greater than or equal to approximately 730,500 PSI/lb/in 3  (182 MPa/g/cm 3 ). For example, the specific strength of the optimized titanium alloy can be greater than or equal to approximately 650,000 PSI/lb/in 3  (162 MPa/g/cm 3 ), greater than or equal to approximately 700,000 PSI/lb/in 3  (174 MPa/g/cm 3 ), greater than or equal to approximately 750,000 PSI/lb/in 3  (187 MPa/g/cm 3 ), greater than or equal to approximately 800,000 PSI/lb/in 3  (199 MPa/g/cm 3 ), greater than or equal to approximately 850,000 PSI/lb/in 3  (212 MPa/g/cm 3 ), greater than or equal to approximately 900,000 PSI/lb/in 3  (224 MPa/g/cm 3 ), greater than or equal to approximately 950,000 PSI/lb/in 3  (237 MPa/g/cm 3 ), greater than or equal to approximately 1,000,000 PSI/lb/in 3  (249 MPa/g/cm 3 ), greater than or equal to approximately 1,050,000 PSI/lb/in 3  (262 MPa/g/cm 3 ), or greater than or equal to approximately 1,100,000 PSI/lb/in 3  (272 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the second material comprising an optimized titanium alloy can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0065, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0075, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0085, greater than or equal to approximately 0.0090, greater than or equal to approximately 0.0095, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, or greater than or equal to approximately 0.0120. 
     In these or other embodiments, the second material comprising an optimized steel can have a specific strength greater than or equal to approximately 500,000 PSI/lb/in 3  (125 MPa/g/cm 3 ), greater than or equal to approximately 510,000 PSI/lb/in 3  (127 MPa/g/cm 3 ), greater than or equal to approximately 520,000 PSI/lb/in 3  (130 MPa/g/cm 3 ), greater than or equal to approximately 530,000 PSI/lb/in 3  (132 MPa/g/cm 3 ), greater than or equal to approximately 540,000 PSI/lb/in 3  (135 MPa/g/cm 3 ), greater than or equal to approximately 550,000 PSI/lb/in 3  (137 MPa/g/cm 3 ), greater than or equal to approximately 560,000 PSI/lb/in 3  (139 MPa/g/cm 3 ), greater than or equal to approximately 570,000 PSI/lb/in 3  (142 MPa/g/cm 3 ), greater than or equal to approximately 580,000 PSI/lb/in 3  (144 MPa/g/cm 3 ), greater than or equal to approximately 590,000 PSI/lb/in 3  (147 MPa/g/cm 3 ), greater than or equal to approximately 600,000 PSI/lb/in 3  (149 MPa/g/cm 3 ), greater than or equal to approximately 625,000 PSI/lb/in 3  (156 MPa/g/cm 3 ), greater than or equal to approximately 675,000 PSI/lb/in 3  (168 MPa/g/cm 3 ), greater than or equal to approximately 725,000 PSI/lb/in 3  (181 MPa/g/cm 3 ), greater than or equal to approximately 775,000 PSI/lb/in 3  (193 MPa/g/cm 3 ), greater than or equal to approximately 825,000 PSI/lb/in 3  (205 MPa/g/cm 3 ), greater than or equal to approximately 875,000 PSI/lb/in 3  (218 MPa/g/cm 3 ), greater than or equal to approximately 925,000 PSI/lb/in 3  (230 MPa/g/cm 3 ), greater than or equal to approximately 975,000 PSI/lb/in 3  (243 MPa/g/cm 3 ), greater than or equal to approximately 1,025,000 PSI/lb/in 3  (255 MPa/g/cm 3 ), greater than or equal to approximately 1,075,000 PSI/lb/in 3  (268 MPa/g/cm 3 ), or greater than or equal to approximately 1,125,000 PSI/lb/in 3  (280 MPa/g/cm 3 ). 
     Further, in these or other embodiments, the second material comprising an optimized steel can have a specific flexibility greater than or equal to approximately 0.0060, greater than or equal to approximately 0.0062, greater than or equal to approximately 0.0064, greater than or equal to approximately 0.0066, greater than or equal to approximately 0.0068, greater than or equal to approximately 0.0070, greater than or equal to approximately 0.0072, greater than or equal to approximately 0.0076, greater than or equal to approximately 0.0080, greater than or equal to approximately 0.0084, greater than or equal to approximately 0.0088, greater than or equal to approximately 0.0092, greater than or equal to approximately 0.0096, greater than or equal to approximately 0.0100, greater than or equal to approximately 0.0105, greater than or equal to approximately 0.0110, greater than or equal to approximately 0.0115, greater than or equal to approximately 0.0120, greater than or equal to approximately 0.0125, greater than or equal to approximately 0.0130, greater than or equal to approximately 0.0135, greater than or equal to approximately 0.0140, greater than or equal to approximately 0.0145, or greater than or equal to approximately 0.0150. 
     In these embodiments, the increased specific strength and/or increased specific flexibility of the optimized second material allow the body  902 , or portions thereof, to be thinned, while maintaining durability. Thinning of the body  902  can reduce club head weight, thereby increasing discretionary weight to be strategically positioned in other areas of the club head  900  to position the head CG low and back and/or increase the club head moment of inertia. 
     iii. Removable Weights 
     In some embodiments, the club head  900  can include one or more weight structures  980  comprising one or more removable weights  982 . The one or more weight structures  980  and/or the one or more removable weights  982  can be located towards the sole  918  and towards the back end  910 , thereby positioning the discretionary weight on the sole  918  and near the back end  910  of the club head  900  to achieve a low and back head CG position. In many embodiments, the one or more weight structures  980  removably receive the one or more removable weights  982 . In these embodiments, the one or more removable weights  982  can be coupled to the one or more weight structures  980  using any suitable method, such as a threaded fastener, an adhesive, a magnet, a snap fit, or any other mechanism capable of securing the one or more removable weights to the one or more weight structures. 
     The weight structure  980  and/or removable weight  982  can be located relative to a clock grid  2000  (illustrated in  FIG. 3 ), which can be aligned with respect to the strikeface  904  when viewed from a top view. The clock grid comprises at least a 12 o&#39;clock ray, a 3 o&#39;clock ray, a 4 o&#39;clock ray, a 5 o&#39;clock ray, a 6 o&#39;clock ray, a 7 o&#39;clock ray, a 8 o&#39;clock ray, and a 9 o&#39;clock ray. For example, the clock grid  2000  comprises a 12 o&#39;clock ray  2012 , which is aligned with the geometric center  940  of the strikeface  904 . The 12 o&#39;clock ray  2012  is orthogonal to the X′Y′ plane. Clock grid  2000  can be centered along 12 o&#39;clock ray  2012 , at a midpoint between the front end  908  and back end  910  of the club head  900 . In the same or other examples, clock grid centerpoint  2010  can be centered proximate to a geometric centerpoint of golf club head  900  when viewed from a bottom view. The clock grid  2000  also comprises a 3 o&#39;clock ray  2003  extending towards the heel  920 , and a 9 o&#39;clock ray  2009  extending towards the toe  922  of the club head  900 . 
     A weight perimeter  984  of the weight structure  980  is located in the present embodiment towards the back end  910 , at least partially bounded between a 4 o&#39;clock ray  2004  and 8 o&#39;clock ray  2008  of clock grid  2000 , while a weight center  986  of a removable weight  982  positioned within weight structure  980  is located between a 5 o&#39;clock ray  2005  and a 7 o&#39;clock ray  2007 . In examples such as the present one, the weight perimeter  984  is fully bounded between the 4 o&#39;clock ray  2004  and the 8 o&#39;clock ray  2008 . Although the weight perimeter  984  is defined external to the club head  900  in the present example, there can be other examples where the weight perimeter  984  may extend into an interior of, or be defined within, the club head  900 . In some examples, the location of the weight structure  980  can be established with respect to a broader area. For instance, in such examples, the weight perimeter  984  of the weight structure  980  can be located towards the back end  910 , at least partially bounded between the 4 o&#39;clock ray  2004  and 9 o&#39;clock ray  2009  of the clock grid  2000 , while the weight center  986  can be located between the 5 o&#39;clock ray  2005  and 8 o&#39;clock ray  2008 . 
     In the present example, the weight structure  9800  protrudes from the external contour of the sole  918 , and is thus at least partially external to allow for greater adjustment of the head CG  970 . In some examples, the weight structure  980  can comprise a mass of approximately 2 grams to approximately 50 grams, and/or a volume of approximately 1 cc to approximately 30 cc. In other examples, the weight structure  980  can remain flush with the external contour of the body  902 . 
     In many embodiments, the removable weight  982  can comprise a mass of approximately 0.5 grams to approximately 30 grams, and can be replaced with one or more other similar removable weights to adjust the location of the head CG  970 . In the same or other examples, the weight center  986  can comprise at least one of a center of gravity of the removable weight  982 , and/or a geometric center of removable weight  982 . 
     iv. Embedded Weights 
     In some embodiments, the club head  900  can include one or more embedded weights to position the discretionary weight on the sole  918 , in the skirt  928 , and/or near the back end  910  of the club head  900  to achieve a low and back head CG position. The one or more embedded weights of club head  900  can be similar or identical to the one or more embedded weights  383  of club head  300 , the one or more embedded weights of club head  500 , or the one or more embedded weights of club head  700 . In many embodiments, the one or more embedded weights are permanently fixed to or within the club head  900 . In these embodiments, the embedded weight can be similar to the high density metal piece (HDMP) described in U.S. Provisional Patent Appl. No. 62/372,870, entitled “Embedded High Density Casting.” 
     In many embodiments, the one or more embedded weights are positioned near the back end  910  of the club head  900 . For example, a weight center of the embedded weight can be located between the 5 o&#39;clock ray  2005  and 7 o&#39;clock ray  2007 , or between the 5 o&#39;clock ray  2005  and 8 o&#39;clock ray  2008  of the clock grid  2000 . In many embodiments, the one or more embedded weights can be positioned on the skirt  928  and near the back end  910  of the club head  900 , on the sole  918  and near the back end  910  of the club head  900 , or on the skirt  928  and the sole  918  near the back end  910  of the club head  900 . 
     In many embodiments, the weight center of the one or more embedded weights is positioned within 0.10 inches, within 0.20 inches, within 0.30 inches, within 0.40 inches, within 0.50 inches, within 0.60 inches, within 0.70 inches, within 0.80 inches, within 0.90 inches, within 1.0 inches, within 1.1 inches, within 1.2 inches, within 1.3 inches, within 1.4 inches, or within 1.5 inches of a perimeter of the club head  900  when viewed from a top view. In these embodiments, the proximity of the embedded weight to the perimeter of the club head  900  can maximize the low and back head CG position, the crown-to-sole moment of inertia I xx , and/or the heel-to-toe moment of inertia I yy . 
     In many embodiments, the weight center of the one or more embedded weights is positioned at a distance from the head CG  970  greater than 1.6 inches, greater than 1.7 inches, greater than 1.8 inches, greater than 1.9 inches, greater than 2.0 inches, greater than 2.1 inches, greater than 2.2 inches, greater than 2.3 inches, greater than 2.4 inches, greater than 2.5 inches, greater than 2.6 inches, greater than 2.7 inches, greater than 2.8 inches, greater than 2.9 inches, or greater than 3.0 inches. 
     In many embodiments, the weight center of the one or more embedded weights is positioned at a distance from the geometric center  940  of the strikeface  904  greater than 4.0 inches, greater than 4.1 inches, greater than 4.2 inches, greater than 4.3 inches, greater than 4.4 inches, greater than 4.5 inches, greater than 4.6 inches, greater than 4.7 inches, greater than 4.8 inches, greater than 4.9 inches, or greater than 5.0 inches. 
     In many embodiments, the one or more embedded weights can comprise a mass between 3.0-120 grams. For example, in some embodiments, the one or more embedded weights can comprise a mass between 3.0-25 grams, between 10-40 grams, between 20-50 grams, between 30-60 grams, between 40-70 grams, between 50-80 grams, between 60-90 grams, between 70-100 grams, between 80-120 grams, or between 90-120 grams. In embodiments where the one or more embedded weights include more than one weight, each of the embedded weights can comprise the same or a different mass. 
     In many embodiments, the one or more embedded weights can comprise a material having a specific gravity between 10.0-22.0. For example, in many embodiments, the one or more embedded weights can comprise a material having a specific gravity greater than 10.0, greater than 11.0, greater than 12.0, greater than 13.0, greater than 14.0, greater than 15.0, greater than 16.0, greater than 17.0, greater than 18.0, or greater than 19.0. In embodiments where the one or more embedded weights include more than one weight, each of the embedded weights can comprise the same or a different material. 
     v. Steep Crown Angle 
     In some embodiments, the golf club head  900  can further include a steep crown angle  988  to achieve the low and back head CG position. The steep crown angle  988  positions the back end of the crown  916  toward the sole  918  or ground, thereby lowering the club head CG position. 
     The crown angle  988  is measured as the acute angle between a crown axis  1090  and the front plane  1020 . In these embodiments, the crown axis is located in a cross-section of the club head taken along a plane positioned perpendicular to the ground plane  1030  and the front plane  1020 . The crown axis  1090  can be further described with reference to a top transition boundary and a rear transition boundary. 
     The club head  900  includes a top transition boundary extending between the front end  908  and the crown  916  from near the heel  920  to near the toe  922 . The top transition boundary includes a crown transition profile  990  when viewed from a side cross sectional view taken along a plane perpendicular to the front plane  1020  and perpendicular to the ground plane  1030  when the club head  900  is at an address position. The side cross sectional view can be taken along any point of the club head  900  from near the heel  920  to near the toe  930 . The crown transition profile defines a front radius of curvature  992  extending from the front end  908  of the club head  900  where the contour departs from the roll radius and/or the bulge radius of the strikeface  904  to a crown transition point  994  indicating a change in curvature from the front radius of curvature  992  to the curvature of the crown  916 . In some embodiments, the front radius of curvature  992  comprises a single radius of curvature extending from the top end  993  of the strikeface perimeter  942  near the crown  916  where the contour departs from the roll radius and/or the bulge radius of the strikeface  904  to a crown transition point  994  indicating a change in curvature from the front radius of curvature  992  to one or more curvatures of the crown  916 . 
     The club head  900  further includes a rear transition boundary extending between the crown  916  and the skirt  928  from near the heel  920  to near the toe  922 . The rear transition boundary includes a rear transition profile  996  when viewed from a side cross sectional view taken along a plane perpendicular to the front plane  1020  and perpendicular to the ground plane  1030  when the club head  900  is at an address position. The cross sectional view can be taken along any point of the club head from near the heel  920  to near the toe  922 . The rear transition profile defines a rear radius of curvature  998  extending from the crown  916  to the skirt  928  of the club head  900 . In many embodiments, the rear radius of curvature  998  comprises a single radius of curvature that transitions the crown  916  to the skirt  928  of the club head  300  along the rear transition boundary. A first rear transition point  1002  is located at the junction between the crown  916  and the rear transition boundary. A second rear transition point  1003  is located at the junction between the rear transition boundary and the skirt  928  of the club head  900 . 
     The front radius of curvature  992  of the top transition boundary can remain constant, or can vary from near the heel  920  to near the toe  922  of the club head  900 . Similarly, the rear radius of curvature  998  of the rear transition boundary can remain constant, or can vary from near the heel  920  to near the toe  922  of the club head  900 . 
     The crown axis  1090  extends between the crown transition point  994  near the front end  908  of the club head  900  and the rear transition point  1002  near the back end  910  of the club head  900 . The crown angle  988  can remain constant, or can vary from near the heel  920  to near the toe  922  of the club head  900 . For example, the crown angle  988  can vary when the side cross sectional view is taken at different locations relative to the heel  920  and the toe  922 . 
     In many embodiments, reducing the crown angle  988  compared to current club heads generates a steeper crown or a crown positioned closer to the ground plane when the club head is at an address position. Accordingly, the reduced crown angle  988  can result in a lower head CG position compared to a club head with a higher crown angle. 
     vi. Hosel Sleeve Weight 
     In some embodiments, the head CG height  974  and/or head CG depth  972  can be achieved by reducing the mass of the hosel sleeve  934 . Removing excess weight from the hosel sleeve  934  results in increased discretionary weight that can be strategically repositioned to regions of the club head  900  to achieve the desired low and back club head CG position. 
     Reducing the mass of the hosel sleeve  934  can be achieve by thinning the sleeve walls, reducing the height of the hosel sleeve  934 , reducing the diameter of the hosel sleeve  934 , and/or by introducing voids in the walls of the hosel sleeve  934 . In many embodiments, the mass of the hosel sleeve  934  can be less than 6 grams, less than 5.5 grams, less than 5.0 grams, less than 4.5 grams, or less than 4.0 grams. In many embodiments, the club head  900  having the reduced mass hosel sleeve can result in a lower (close to the sole) and farther back (closer to the back end) club head CG position than a similar club head with a heavier hosel sleeve. 
     B. Aerodynamic Drag 
     In many embodiments, the club head  900  comprises a low and back club head CG position and an increased club head moment of inertia, in combination with reduced aerodynamic drag. 
     In many embodiments, the club head  900  experiences an aerodynamic drag force less than approximately 1.0 lbf, less than 0.90 lbf, less than 0.80 lbf, less than 0.75 lbf, less than 0.70 lbf, less than 0.65 lbf, or less than 0.60 lbf when tested in a wind tunnel with a squared face and an air speed of 95 miles per hour (mph). In these or other embodiments, the club head  900  experiences an aerodynamic drag force less than approximately 1.0 lbf, less than 0.90 lbf, less than 0.80 lbf, less than 0.75 lbf, less than 0.70 lbf, less than 0.65 lbf, or less than 0.60 lbf when simulated using computational fluid dynamics with a squared face and an air speed of 95 miles per hour (mph). In these embodiments, the airflow experienced by the club head  900  having the squared face is directed at the strikeface  904  in a direction perpendicular to the X′Y′ plane. The club head  900  having reduced aerodynamic drag can be achieved using various means, as described below. 
     i. Crown Angle Height 
     In some embodiments, reducing the crown angle  988  to form a steeper crown and lower head CG position may result in an undesired increase in aerodynamic drag due to increased air flow separation over the crown during a swing. To prevent increased drag associated with a reduced crown angle  988 , a maximum crown height  1004  can be increased. The maximum crown height  1004  is the greatest distance between the crown  916  and the crown axis  1090  taken at any side cross sectional view of the club head along a plane positioned parallel to the Y′Z′ plane. In many embodiments, a greater maximum crown height  1004  results in the crown  916  having a greater curvature. A greater curvature in the crown  916  moves the location of the air flow separation during a swing further back on the club head  900 . In other words, a greater curvature allows the airflow to stay attached to club head  900  for a longer distance along the crown  916  during a swing. Moving the airflow separation point back on the crown  916  can result in reduced aerodynamic drag and increased club head swing speeds, thereby resulting in increased ball speed and distance. 
     ii. Transition Profiles 
     In many embodiments, the transition profiles of the club head  900  from the strikeface  904  to the crown  916 , the strikeface  904  to the sole  918 , and/or the crown  916  to the sole  918  along the back end  910  of the club head  900  can affect the aerodynamic drag on the club head  900  during a swing. 
     In some embodiments, the club head  900  having the top transition boundary defining the crown transition profile  990 , and the rear transition boundary defining the rear transition profile  996  further includes a sole transition boundary defining a sole transition profile  1001 . The sole transition boundary extends between the front end  908  and the sole  918  from near the heel  920  to near the toe  922 . The sole transition boundary includes a sole transition profile  1001  when viewed from a side cross sectional view taken along a plane parallel to the Y′Z′ plane. The side cross sectional view can be taken along any point of the club head from near the heel  920  to near the toe  922 . The sole transition profile  1001  defines a sole radius of curvature  1012  extending from the front end  908  of the club head  900  where the contour departs from the roll radius and/or the bulge radius of the strikeface  904  to a sole transition point  1014  indicating a change in curvature from sole radius of curvature  1012  to the curvature of the sole  918 . In some embodiments, the sole radius of curvature  1012  comprises a single radius of curvature extending from the bottom end  1013  of the strikeface perimeter  942  near the sole  1018  where the contour departs from the roll radius and/or the bulge radius of the strikeface  904  to a sole transition point  1014  indicating a change in curvature from the sole radius of curvature  1012  to a curvature of the sole  1014 . 
     In many embodiments, the crown transition profile  990 , the sole transition profile  1001 , and the rear transition profile  996  can be similar to the crown transition, sole transition, and rear transition profiles described in U.S. patent Ser. No. 15/233,486, entitled “Golf Club Head with Transition Profiles to Reduce Aerodynamic Drag.” Further, the front radius of curvature  992  can be similar to the first crown radius of curvature, the sole radius of curvature  1012  can be similar to the first sole radius of curvature, and the rear radius of curvature  998  can be similar to the rear radius of curvature described U.S. patent Ser. No. 15/233,486, entitled “Golf Club Head with Transition Profiles to Reduce Aerodynamic Drag.” 
     iii. Turbulators 
     In some embodiments, the club head  900  can further include a plurality of turbulators  914 , as described in U.S. patent application Ser. No. 13/536,753, now U.S. Pat. No. 8,608,587, granted on Dec. 17, 2013, entitled “Golf Club Heads with Turbulators and Methods to Manufacture Golf Club Heads with Turbulators,” which is incorporated fully herein by reference. In many embodiments, the plurality of turbulators  914  disrupt the airflow thereby creating small vortices or turbulence inside the boundary layer to energize the boundary layer and delay separation of the airflow on the crown during a swing. 
     In some embodiments, the plurality of turbulators  614  can be adjacent to the crown transition point  394  of the club head  900 . The plurality of turbulators  914  project from an outer surface of the crown  916  and include a length extending between the front end  908  and the back end  910  of the club head  900 , and a width extending from the heel  920  to the toe  922  of the club head  900 . In many embodiments, the length of the plurality of turbulators  914  is greater than the width. In some embodiments, the plurality of turbulators  914  can comprise the same width. In some embodiments, the plurality of turbulators  914  can vary in height profile. In some embodiments, the plurality of turbulators  914  can be higher toward the apex of the crown  916  than in comparison to the front of the crown  916 . In other embodiments, the plurality of turbulators  914  can be higher toward the front of the crown  916 , and lower in height toward the apex of the crown  916 . In other embodiments, the plurality of turbulators  914  can comprise a constant height profile. Further, in many embodiments, at least a portion of at least one turbulator is located between the strikeface and an apex of the crown  916 , and the spacing between adjacent turbulators is greater than the width of each of the adjacent turbulators. 
     iv. Back Cavity 
     In some embodiments, the club head  900  can further include a cavity  1020  located at the back end  910  and in the trailing edge  928  of the club head  900 , similar to the cavity described in U.S. patent application Ser. No. 14/882,092, entitled “Golf Club Heads with Aerodynamic Features and Related Methods.” In many embodiments, the cavity  1024  can break the vortices generated behind golf club head  900  into smaller vortices to reduce the size of the wake and/or reduce drag. In some embodiments, breaking the vortices into smaller vortices can generate a region of high pressure behind golf club head  900 . In some embodiments, this region of high pressure can push golf club head  900  forward, reduce drag, and/or enhance the aerodynamic design of golf club head  900 . In many embodiments, the net effect of smaller vortices and reduced drag is an increase in the speed of golf club head  900 . This effect can lead to higher speeds at which a golf ball leaves strikeface after impact to increase ball travel distance. 
     In many embodiments, the cavity  1020  includes a back wall  1022  that is oriented in a direction perpendicular to the X′Z′ plane and includes a width measured in a direction from the heel  920  to the toe  922 , a depth  1024 , and a height  1026 . 
     v. Hosel Structure 
     In some embodiments, the hosel structure  930  can have a smaller outer diameter to reduce the aerodynamic drag on the club head  900  during a swing, compared to a similar club head having a larger diameter hosel structure. In many embodiments, the hosel structure  930  has an outer diameter less than 0.53 inches. For example, the hosel structure  930  can have an outer diameter less than 0.60 inches, less than 0.59 inches, less than 0.58 inches, less than 0.57 inches, less than 0.56 inches, less than 0.55 inches, less than 0.54 inches, less than 0.53 inches, less than 0.52, less than 0.51 inches, or less than 0.50 inches. In many embodiments, the outer diameter of the hosel structure  930  is reduced while maintaining adjustability of the loft angle and/or lie angle of the club head  900 . 
     C. Balance of CG Position, Moment of Inertia, and Aerodynamic Drag 
     In current golf club head design, increasing or maximizing the moment of inertia of the club head can adversely affect other performance characteristics of the club head, such as aerodynamic drag. The club head  900  described herein increases or maximizes the club head moment of inertia, while simultaneously maintaining or reducing aerodynamic drag. Accordingly, the club head  900  having improved impact performance characteristics (e.g. spin, launch angle, ball speed, and forgiveness) also balances or improves swing performance characteristics (e.g. aerodynamic drag, ability to square the club head at impact, and swing speed). 
     V. Method of Manufacturing 
     In many embodiments, a method for forming the club head  100  can comprise forming a body  102 , forming a strikeface  104 , and coupling the strikeface  104  to the body  102  to form the club head  100 . In many embodiments, forming the body  102  can consist of casting, 3D printing, machining, or any other suitable method for forming the body  102 . In some embodiments, the body can be formed as a unitary piece. In other embodiments, the body  102  can be formed of a plurality of components that are coupled to form the body  102 . 
     In many embodiments, forming the strikeface  104  can consist of machining, 3D printing, casting, or otherwise forming the strike face  104 . In many embodiments, coupling the strikeface  104  and the body  102  can be accomplished by welding, mechanical fastening, or any other suitable method of coupling the strikeface  104  and the body  102 . 
     VI. EXAMPLES 
     Example 1 
     Described herein is an exemplary golf club head  300  having a volume of 466 cc, a depth  360  of 4.81 inches, a length  362  of 4.88 inches, and a height  364  of 2.65 inches. The exemplary club head  300  includes a plurality of thin regions  376  on the crown  316  comprising 57% of the surface area of the crown  316  and having a minimum thickness of 0.013 inch. The exemplary club head  300  further includes a crown angle  388  of 68.6 degrees and a crown angle height  404  of 0.522 inch. 
     The exemplary club head  300  includes an embedded weight  383  comprising tungsten having a specific gravity of between 14-15 and a mass of 14.5 grams. In this example, the distance from the weight center  387  of the embedded weight  383  to the perimeter of the club head  300  is 0.183 inch when viewed from a top or bottom view. Further, in this example, the distance from the weight center  387  to the head CG  370  is 2.67 inches, and the distance from the weight center  387  to the geometric center  340  of the strikeface  304  is 4.58 inches. The exemplary club head  300  further includes a weight structure  380  that houses a removable weight  382 . In this example, the weight structure  380  protrudes at least partially from an external contour of the sole  318 . Further still, the exemplary club head  300  includes a hosel sleeve  334  having a mass of 4.5 grams. 
     As a result of the above described and/or additional parameters, the exemplary club head  300  comprises a head CG depth  372  of 1.87 inches and a head CG height  374  of 0.083 inches. Further, as a result of the above described and/or additional parameters, the exemplary club head  300  comprises a crown-to-sole moment of inertia I xx  of 4258 g·cm 2 , a heel-to-toe moment of inertia I yy  of 5710 g·cm 2 , and a combined moment of inertia I xx +I yy  of 9968 g·cm 2 . 
     The exemplary club head  300  further includes a front radius of curvature  392  of 0.24 inch, a sole radius of curvature  412  of 0.30 inch, and a rear radius of curvature  398  of 0.20 inch. Further, the exemplary club head  300  includes a front projected area of 6.73 in 2  (0.00434 m 2 ), a side projected area of 8.73 in 2  (0.00563 m 2 ), and a hosel structure  330  having an outer diameter of 0.54 inch. As a result of the these and/or additional parameters, the exemplary club head  300  comprises an aerodynamic drag force of 0.95 lbf when simulated using computational fluid dynamics with a squared face at an air speed of 102 miles per hour (mph). 
     Example 2 
     Described herein is an exemplary golf club head  500  having a volume of 445 cc, a depth  560  of 4.64 inches, a length  562  of 4.77 inches, and a height  564  of 2.66 inches. The exemplary club head  500  includes a plurality of thin regions  576  on the crown  316  comprising 55% of the surface area of the crown  516  and having a minimum thickness of 0.013 inch. The exemplary club head  500  further includes a crown angle  588  of 70.0 degrees and a crown angle height  604  of 0.543 inch. 
     The exemplary club head  500  includes an embedded weight  583  comprising tungsten having a specific gravity of between 15-17 and a mass of 7 grams. In this example, the distance from the weight center  587  of the embedded weight  583  to the perimeter of the club head  500  is 0.274 inch when viewed from a top or bottom view. Further, in this example, the distance from the weight center  587  to the head CG  570  is 2.58 inches, and the distance from the weight center  587  to the geometric center  540  of the strikeface  504  is 4.31 inches. The exemplary club head  500  further includes a weight structure  580  that houses a removable weight  582 . In this example, the weight structure  580  protrudes at least partially from an external contour of the sole  518 . Further still, the exemplary club head  500  includes a hosel sleeve  534  having a mass of 4.5 grams. 
     As a result of the above described and/or additional parameters, the exemplary club head  500  comprises a head CG depth  572  of 1.70 inches and a head CG height  574  of 0.113 inches. Further, as a result of the above described and/or additional parameters, the exemplary club head  500  comprises a crown-to-sole moment of inertia I xx  of 3768 g·cm 2 , a heel-to-toe moment of inertia I yy  of 5379 g·cm 2 , and a combined moment of inertia I xx +I yy  of 9147 g·cm 2 . 
     The exemplary club head  500  further includes a front radius of curvature  592  of 0.24 inch, a sole radius of curvature  612  of 0.30 inch, and a rear radius of curvature  598  of 0.20 inch. Further, the exemplary club head  500  includes a front projected area of 6.40 in 2  (0.00413 m 2 ), a side projected area of 8.18 in 2  (0.00528 m 2 ), and a hosel structure  530  having an outer diameter of 0.54 inch. Further still, the exemplary club head  500  includes a back cavity  620  having a length of 1.7 inches, a height  626  of 0.215 inch, and a depth  624  of 0.75 inch. As a result of the these and/or additional parameters, the exemplary club head  500  comprises an aerodynamic drag force of 0.83 lbf when simulated using computational fluid dynamics with a squared face at an air speed of 102 miles per hour (mph). 
     Replacement of one or more claimed elements constitutes reconstruction and not repair. Additionally, benefits, other advantages, and solutions to problems have been described with regard to specific embodiments. The benefits, advantages, solutions to problems, and any element or elements that may cause any benefit, advantage, or solution to occur or become more pronounced, however, are not to be construed as critical, required, or essential features or elements of any or all of the claims. 
     As the rules to golf may change from time to time (e.g., new regulations may be adopted or old rules may be eliminated or modified by golf standard organizations and/or governing bodies such as the United States Golf Association (USGA), the Royal and Ancient Golf Club of St. Andrews (R&amp;A), etc.), golf equipment related to the apparatus, methods, and articles of manufacture described herein may be conforming or non-conforming to the rules of golf at any particular time. Accordingly, golf equipment related to the apparatus, methods, and articles of manufacture described herein may be advertised, offered for sale, and/or sold as conforming or non-conforming golf equipment. The apparatus, methods, and articles of manufacture described herein are not limited in this regard. 
     While the above examples may be described in connection with a driver-type golf club, the apparatus, methods, and articles of manufacture described herein may be applicable to other types of golf club such as a fairway wood-type golf club, a hybrid-type golf club, an iron-type golf club, a wedge-type golf club, or a putter-type golf club. Alternatively, the apparatus, methods, and articles of manufacture described herein may be applicable other type of sports equipment such as a hockey stick, a tennis racket, a fishing pole, a ski pole, etc. 
     Moreover, embodiments and limitations disclosed herein are not dedicated to the public under the doctrine of dedication if the embodiments and/or limitations: (1) are not expressly claimed in the claims; and (2) are or are potentially equivalents of express elements and/or limitations in the claims under the doctrine of equivalents. 
     Various features and advantages of the disclosure are set forth in the following claims.