Patent Publication Number: US-11020639-B2

Title: Golf club having an elastomer element for ball speed control

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 16/286,412, filed Feb. 26, 2019, which is a continuation-in-part of application Ser. No. 16/225,577, filed Dec. 19, 2018, which is a continuation-in-part of application Ser. No. 16/158,578, filed Oct. 12, 2018, now U.S. Pat. No. 10,293,226, which is a continuation-in-part of application Ser. No. 16/027,077, filed Jul. 3, 2018, which is a continuation-in-part of application Ser. No. 15/220,122, filed Jul. 26, 2016, now U.S. Pat. No. 10,086,244, which are hereby incorporated by reference in their entirety. To the extent appropriate, the present application claims priority to the above-referenced applications. 
    
    
     BACKGROUND 
     It is a goal for golfers to reduce the total number of swings needed to complete a round of golf, thus reducing their total score. To achieve that goal, it is generally desirable to for a golfer to have a ball fly a consistent distance when struck by the same golf club and, for some clubs, also to have that ball travel a long distance. For instance, when a golfer slightly mishits a golf ball, the golfer does not want the golf ball to fly a significantly different distance. At the same time, the golfer also does not want to have a significantly reduced overall distance every time the golfer strikes the ball, even when the golfer strikes the ball in the “sweet spot” of the golf club. 
     SUMMARY 
     One non-limiting embodiment of the present technology includes a golf club head including a club head body including a back portion and a striking face; wherein the striking face comprises a front surface configured to strike a golf ball and a rear surface opposite the front surface; wherein the back portion is spaced from the rear surface; a first deformable member residing between the back portion and the rear surface of the striking face; wherein the first deformable member comprises a front surface in contact with the rear surface of the striking face and a rear surface in contact with the back portion; and a second deformable member residing between the back portion and the rear surface of the striking face; wherein the second deformable member comprises a front surface in contact with the rear surface of the striking face and a rear surface in contact with the back portion; and a coordinate system centered at a center of gravity of the golf club head, the coordinate system including a y-axis extending vertically, perpendicular to a ground plane when the golf club head is in an address position at prescribed loft and lie, an x-axis perpendicular to the y-axis and parallel to the striking face, extending towards a heel of the golf club head, and a z-axis, perpendicular to the y-axis and the x-axis and extending through the striking face, wherein the striking face comprises a plurality of scorelines, wherein the striking face comprises a heel reference plane extending parallel to the y-axis and the-x-axis, wherein the heel reference plane is offset 1 millimeter towards the heel from a heel-most extent of the scorelines, wherein the striking face comprises a striking face length measured from the heel reference plane to a toe-most extent of the front surface of the striking face parallel to the x-axis; wherein the rear surface of the striking face comprises a first supported region, wherein a perimeter of the front surface of the first deformable member defines the first supported region, wherein the first supported region comprises a first geometric center, wherein the first geometric center of the first supported region is located a first supported region offset length toward from the heel reference plane measured parallel to the x-axis; wherein the rear surface of the striking face comprises a second supported region, wherein a perimeter of the front surface of the second deformable member defines the second supported region, wherein the second supported region comprises a second geometric center, wherein the second geometric center of the second supported region is located a second supported region offset length toeward from the heel reference plane measured parallel to the x-axis; wherein the first supported region offset length divided by the second supported region offset length is greater than 1.0. 
     In an additional non-limiting embodiment of the present technology the first supported region offset length divided by the second supported region offset length is greater than 1.5. 
     In an additional non-limiting embodiment of the present technology the first supported region offset length divided by the second supported region offset length is greater than 2.0. 
     In an additional non-limiting embodiment of the present technology at least a portion of the striking face comprises a thickness of less than or equal to 2.2 mm. 
     In an additional non-limiting embodiment of the present technology the front surface of the first deformable member is circular having a front diameter, wherein the rear surface of the first deformable member is circular having a rear diameter, wherein the front diameter is less than the rear diameter and wherein the front surface of the second deformable member is circular having a front diameter, wherein the rear surface of the second deformable member is circular having a rear diameter, wherein the front diameter is less than the rear diameter. 
     In an additional non-limiting embodiment of the present technology the first deformable member has a greater Shore A durometer than the second deformable member. 
     In an additional non-limiting embodiment of the present technology the striking face comprises a first density, wherein the back portion comprises a back cover, wherein the back cover comprises a recess, wherein the second deformable member is at least partially retained within the recess, wherein the back cover comprises a second density, wherein the first density is greater than the second density. 
     In an additional non-limiting embodiment of the present technology the center of gravity of the golf club head is located less than or equal to 20 millimeters above the ground plane, measured parallel to the y-axis, and wherein the golf club head comprises an MOI-Y greater than or equal to 250 kg-mm 2 . 
     One non-limiting embodiment of the present technology includes a golf club head including a club head body including a back portion and a striking face; wherein the striking face comprises a front surface configured to strike a golf ball and a rear surface opposite the front surface; wherein the back portion is spaced from the rear surface; a first deformable member residing between the back portion and the rear surface of the striking face; wherein the first deformable member comprises a front surface in contact with the rear surface of the striking face; and a second deformable member residing between the back portion and the rear surface of the striking face; wherein the second deformable member comprises a front surface in contact with the rear surface of the striking face; wherein the first deformable member has a greater Shore A durometer than the second deformable member. 
     In an additional non-limiting embodiment of the present technology the striking face comprises a first density, wherein the back portion comprises a back cover, wherein the back cover comprises a recess, wherein the second deformable member is at least partially retained within the recess, wherein the back cover comprises a second density, wherein the first density is greater than the second density. 
     In an additional non-limiting embodiment of the present technology at least a portion of the striking face comprises a thickness of less than or equal to 2.2 mm. 
     In an additional non-limiting embodiment of the present technology the front surface of the first deformable member is circular having a front diameter, wherein the rear surface of the first deformable member is circular having a rear diameter, wherein the front diameter is less than the rear diameter, wherein the front surface of the second deformable member is circular having a front diameter, wherein the rear surface of the second deformable member is circular having a rear diameter, wherein the front diameter is less than the rear diameter. 
     In an additional non-limiting embodiment of the present technology the golf club head comprises an interior cavity formed between the back portion and the striking face, wherein an aperture is formed through the back portion, an adjustment driver residing within the aperture, the adjustment driver including a recess adjacent the interior cavity, wherein at least a portion of the first deformable member resides within the recess, wherein the back portion comprises a shelf surrounding the aperture and wherein the adjustment driver comprises a flange, the flange in contact with the shelf. 
     An additional non-limiting embodiment of the present technology further includes a coordinate system centered at a center of gravity of the golf club head, the coordinate system including a y-axis extending vertically, perpendicular to a ground plane when the golf club head is in an address position at prescribed loft and lie, an x-axis perpendicular to the y-axis and parallel to the striking face, extending towards a heel of the golf club head, and a z-axis, perpendicular to the y-axis and the x-axis and extending through the striking face, wherein the striking face comprises a plurality of scorelines, wherein the striking face comprises a heel reference plane extending parallel to the y-axis and the-x-axis, wherein the heel reference plane is offset 1 millimeter towards the heel from a heel-most extent of the scorelines, wherein the striking face comprises a striking face length measured from the heel reference plane to a toe-most extent of the front surface of the striking face parallel to the x-axis, wherein the rear surface of the striking face comprises a first supported region, wherein a perimeter of the front surface of the first deformable member defines the first supported region, wherein the first supported region comprises a first geometric center, wherein the first geometric center of the first supported region is located a first supported region offset length toeward from the heel reference plane measured parallel to the x-axis, wherein the rear surface of the striking face comprises a second supported region, wherein a perimeter of the front surface of the second deformable member defines the second supported region, wherein the second supported region comprises a second geometric center, wherein the second geometric center of the second supported region is located a second supported region offset length toeward from the heel reference plane measured parallel to the x-axis, wherein the first supported region offset length divided by the second supported region offset length is greater than 1.5. 
     One non-limiting embodiment of the present technology includes a golf club head including a club head body including a back portion and a striking face; wherein the striking face comprises a front surface configured to strike a golf ball and a rear surface opposite the front surface; wherein the back portion is spaced from the rear surface; a first deformable member residing between the back portion and the rear surface of the striking face; wherein the first deformable member comprises a front surface in contact with the rear surface of the striking face; and a second deformable member residing between the back portion and the rear surface of the striking face; wherein the second deformable member comprises a front surface in contact with the rear surface of the striking face; wherein the back portion comprises a back cover; wherein the back cover comprises a recess; and wherein the second deformable member is at least partially retained within the recess. 
     In an additional non-limiting embodiment of the present technology the striking face comprises a first density, wherein the back cover comprises a second density, wherein the first density is greater than the second density. 
     In an additional non-limiting embodiment of the present technology the first deformable member has a greater Shore A durometer than the second deformable member. 
     In an additional non-limiting embodiment of the present technology at least a portion of the striking face comprises a thickness of less than or equal to 2.2 mm. 
     In an additional non-limiting embodiment of the present technology the front surface of the first deformable member is circular having a front diameter, wherein the rear surface of the first deformable member is circular having a rear diameter, wherein the front diameter is less than the rear diameter, wherein the front surface of the second deformable member is circular having a front diameter, wherein the rear surface of the second deformable member is circular having a rear diameter, wherein the front diameter is less than the rear diameter. 
     In an additional non-limiting embodiment of the present technology the golf club head comprises an interior cavity formed between the back portion and the striking face, wherein an aperture is formed through the back portion, an adjustment driver residing within the aperture, the adjustment driver including a recess adjacent the interior cavity, wherein at least a portion of the first deformable member resides within the recess, wherein the back portion comprises a shelf surrounding the aperture and wherein the adjustment driver comprises a flange, the flange in contact with the shelf. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive examples are described with reference to the following Figures. 
         FIGS. 1A-1B  depict section views of a golf club head having an elastomer element. 
         FIG. 1C  depicts a perspective section view of the golf club head depicted in  FIGS. 1A-1B . 
         FIGS. 2A-2B  depict section views of a golf club head having an elastomer element and a striking face with a thickened center portion. 
         FIGS. 3A-3B  depict section views of a golf club head having an elastomer element and an adjustment mechanism to adjust the compression of the elastomer element. 
         FIG. 4A  depicts a perspective view of another example of a golf club head having an elastomer element and an adjustment mechanism to adjust the compression of the elastomer element. 
         FIG. 4B  depicts a section view of the golf club head of  FIG. 4A . 
         FIG. 4C  depicts a section view of another example of a golf club having an elastomer element and an adjustment mechanism to adjust the compression of the elastomer element. 
         FIG. 5A  depicts a stress contour diagram for a golf club head without an elastomer element. 
         FIG. 5B  depicts a stress contour diagram for a golf club head with an elastomer element. 
         FIG. 6A  depicts a front view of the golf club head. 
         FIG. 6B  depicts a toe view of the golf club head of  FIG. 6A . 
         FIG. 6C  depicts a section view A-A of the golf club head of  FIG. 6A . 
         FIG. 6D  depicts a perspective view of the golf club head of  FIG. 6A  oriented perpendicular to the striking face. 
         FIG. 6E  depicts a perspective view of the golf club head of  FIG. 6A  oriented perpendicular to the striking face including the supported region. 
         FIG. 7A  depicts a perspective view of the golf club head. 
         FIG. 7B  depicts an additional perspective view of the golf club head of  FIG. 7A . 
         FIG. 7C  depicts a rear view of the golf club head of  FIG. 7A . 
         FIG. 8A  depicts a section view B-B of the golf club head of  FIG. 7C . 
         FIG. 8B  depicts a section view C-C of the golf club head of  FIG. 7C . 
         FIG. 8C  depicts a section view D-D of the golf club head of  FIG. 7C . 
         FIG. 9A  depicts an additional section view of the front of the golf club head of  FIG. 7A  missing the striking face. 
         FIG. 9B  depicts the section view from  FIG. 9A  with the deformable member removed. 
         FIG. 10  depicts a perspective view of the golf club head of  FIG. 7A  oriented perpendicular to the striking face including the supported region. 
         FIG. 11A  depicts a cross sectional view of the golf club head of  FIG. 7C  including an additional embodiment of an elastomer element. 
         FIG. 11B  depicts a cross sectional view of the golf club head of  FIG. 7C  including an additional embodiment of an elastomer element. 
         FIG. 11C  depicts a cross sectional view of the golf club head of  FIG. 7C  including an additional embodiment of an elastomer element. 
         FIG. 11D  depicts a cross sectional view of the golf club head of  FIG. 7C  including an additional embodiment of an elastomer element. 
         FIG. 12A  depicts the periodogram power spectral density estimate of the golf club head depicted in  FIG. 11A . 
         FIG. 12B  depicts the sound power estimate of the golf club head depicted in  FIG. 11A . 
         FIG. 13A  depicts the periodogram power spectral density estimate of the golf club head depicted in  FIG. 11D . 
         FIG. 13B  depicts the sound power estimate of the golf club head depicted in  FIG. 11D . 
         FIG. 14A  illustrates a cross sectional view of an elastomer element having a larger rear portion than front portion. 
         FIG. 14B  illustrates a cross sectional view of an elastomer element having a larger rear portion than front portion. 
         FIG. 14C  illustrates a cross sectional view of an elastomer element having a larger rear portion than front portion. 
         FIG. 14D  illustrates a cross sectional view of an elastomer element similar to that of  FIG. 14A  but includes a first material and a second material. 
         FIG. 14E  illustrates a cross sectional view of an elastomer element similar to that of  FIG. 14B  but includes a first material and a second material. 
         FIG. 14F  illustrates a cross sectional view of an elastomer element similar to that of  FIG. 14C  but includes a first material and a second material. 
         FIG. 14G  illustrates a cross sectional view of an elastomer element similar to that of  FIG. 14A  but the center of the front portion is offset from a center of the rear portion. 
         FIG. 14H  illustrates a cross sectional view of an elastomer element similar to that of  FIG. 14B  but the center of the front portion is offset from a center of the rear portion. 
         FIG. 14I  illustrates a cross sectional view of an elastomer element similar to that of  FIG. 14C  but the center of the front portion is offset from a center of the rear portion. 
         FIG. 14J  illustrates a cross sectional view of an elastomer element which necks down in diameter between the front portion and the rear portion. 
         FIG. 14K  illustrates a cross sectional view of an elastomer element which necks down in diameter between the front portion and the rear portion. 
         FIG. 14L  illustrates a cross sectional view of an elastomer element similar to that of  FIG. 14J  but includes a first material and a second material. 
         FIG. 15A  depicts a rear view of the golf club head. 
         FIG. 15B  depicts a perspective view of the golf club head of  FIG. 15A . 
         FIG. 15C  depicts an additional perspective view of the golf club head of  FIG. 15A . 
         FIG. 15D  depicts a section view E-E of the golf club head of  FIG. 15A . 
         FIG. 16  depicts the section view E-E of the golf club head of  FIG. 15D  without the adjustment driver and elastomer element installed. 
         FIG. 17A  depicts a perspective view of the adjustment driver and elastomer element of the golf club head of  FIG. 15A . 
         FIG. 17B  depicts an additional perspective view of the adjustment driver and elastomer element of the golf club head of  FIG. 15A . 
         FIG. 17C  depicts a side view of the adjustment driver and elastomer element of the golf club head of  FIG. 15A . 
         FIG. 17D  depicts a section view of the adjustment driver and elastomer element of  FIG. 17A . 
         FIG. 17E  depicts an additional perspective of the section view of the adjustment driver and elastomer element of  FIG. 17A . 
         FIG. 18  depicts a rear view of the golf club head. 
         FIG. 19  depicts an exploded view of the golf club head of  FIG. 18 . 
         FIG. 20  depicts a section view F-F of the golf club head. 
         FIG. 21  depicts a section view G-G of the golf club head. 
         FIG. 22  depicts a frontal view of the golf club head of  FIG. 18 , including the supported regions. 
         FIG. 23  depicts a perspective view of golf club head and an additional embodiment of the second deformable member. 
         FIG. 24  depicts the second deformable member illustrated in  FIG. 23 . 
         FIG. 25  depicts a section view F-F of the golf club head including the second deformable member illustrated in  FIGS. 23 and 24 . 
     
    
    
     DETAILED DESCRIPTION 
     The technologies described herein contemplate an iron-type golf club head that incorporates an elastomer element to promote more uniform ball speed across the striking face of the golf club. Traditional thin-faced iron-type golf clubs generally produce less uniform launch velocities across the striking face due to increased compliance at the geometric center of the striking face. For example, when a golf club strikes a golf ball, the striking face of the club deflects and then springs forward, accelerating the golf ball off the striking face. While such a design may lead to large flight distances for a golf ball when struck in the center of the face, any off-center strike of golf ball causes significant losses in flight distance of the golf ball. In comparison, an extremely thick face causes more uniform ball flight regardless of impact location, but a significant loss in launch velocities. The present technology incorporates an elastomer element between a back portion of the hollow iron and the rear surface of the striking face. By including the elastomer element, the magnitude of the launch velocity may be reduced for strikes at the center of the face while improving uniformity of launch velocities across the striking face. In some examples, the compression of the elastomer element between the back portion and the striking face may also be adjustable to allow for a golfer or golf club fitting professional to alter the deflection of the striking face when striking a golf ball. 
       FIGS. 1A-1B  depict section views depict section views of a golf club head  100  having an elastomer element  102 .  FIG. 1C  depicts a perspective section view of the golf club head  100 .  FIGS. 1A-1C  are described concurrently. The club head  100  includes a striking face  118  and a back portion  112 . A cavity  120  is formed between the striking face  118  and the back portion  112 . An elastomer element  102  is disposed in the cavity  120  between the striking face  118  and the back portion  112 . A rear portion of the elastomer element  102  is held in place by a cradle  108 . The cradle  108  is attached to the back portion  112  of the golf club head  100 , and the cradle  108  includes a recess  109  to receive the rear portion of the elastomer element  102 . The lip of the cradle  108  prevents the elastomer element  102  from sliding or otherwise moving out of position. The elastomer element  102  may have a generally frustoconical shape, as shown in  FIGS. 1A-1B . 
     In other examples, the elastomer element  102  may have a cylindrical, spherical, cuboid, or prism shape. The recess  109  of the cradle  108  is formed to substantially match the shape of the rear portion of the elastomer element  102 . For example, with the frustoconical elastomer element  102 , the recess  109  of the cradle  108  is also frustoconical such that the surface of the rear portion of the elastomer element  102  is in contact with the interior walls of the recess  109  of the cradle  108 . The cradle  108  may be welded or otherwise attached onto the back portion  112 , or the cradle  108  may be formed as part of the back portion  112  during a casting or forging process. The back portion  112  may also be machined to include the cradle  108 . 
     A front portion  103  of the elastomer element  102  contacts the rear surface  119  of the striking face  118 . The front portion  103  of the elastomer element  102  may be held in place on the rear surface  119  of the striking face  118  by a securing structure, such as flange  110 . The flange  110  protrudes from the rear surface  119  of the striking face  118  into the cavity  120 . The flange  110  receives the front portion  103  of the elastomer element  102  to substantially prevent the elastomer element  102  from sliding along the rear surface  119  of the striking face  118 . The flange  110  may partially or completely surround the front portion  103  of the elastomer element  102 . Similar to the cradle  108 , the flange  110  may be shaped to match the shape of the front portion  103  of the elastomer element  102  such that the surface of the front portion  103  of the elastomer element  102  is in contact with the interior surfaces of the flange  110 . The flange  110  may be welded or otherwise attached to the rear surface  119  of the striking face  118 . The flange  110  may also be cast or forged during the formation of the striking face  118 . For instance, where the striking face  118  is a face insert, the flange  110  may be incorporated during the casting or forging process to make the face insert. In another example, the flange  110  and the striking face  118  may be machined from a thicker face plate. Alternative securing structures other than the flange  110  may also be used. For instance, two or more posts may be included on rear surface  119  of the striking face  118  around the perimeter of the front portion  103  of the elastomer element  102 . As another example, an adhesive may be used to secure the elastomer element  102  to the rear surface  119  of the striking face  118 . In other embodiments, no securing structure is utilized and the elastomer element  102  is generally held in place due to the compression of the elastomer element  102  between the cradle  108  and the rear surface  119  of the striking face  118 . 
     In the example depicted in  FIGS. 1A-1C , the elastomer element  102  is disposed behind the approximate geometric center of the striking face  118 . In traditional thin face golf clubs, strikes at the geometric center of the striking face  118  display the largest displacement of the striking face  118 , and thus the greatest ball speeds. By disposing the elastomer  102  at the geometric center of the striking face  118 , the deflection of the striking face  118  at that point is reduced, thus reducing the ball speed. Portions of the striking face  118  not backed by the elastomer element  102 , however, continue to deflect into the cavity  120  contributing to the speed of the golf ball. As such, a more uniform distribution of ball speeds resulting from ball strikes across the striking face  118  from the heel to the toe may be achieved. In other examples, the elastomer element  102  may be disposed at other locations within the club head  100 . 
     The elasticity of the elastomer element  102  also affects the deflection of the striking face  118 . For instance, a material with a lower elastic modulus allows for further deflection of the striking face  118 , providing for higher maximum ball speeds but less uniformity of ball speeds. In contrast, a material with a higher elastic modulus further prevents deflection of the striking face  118 , providing for lower maximum ball speeds but more uniformity of ball speeds. Different types of materials are discussed in further detail below with reference to Tables 2-3. 
     The golf club head  100  also includes a sole  105  having a sole channel  104  in between a front sole portion  114  and a rear sole portion  116 . The sole channel  104  extends along the sole  105  of the golf club head  100  from a point near the heel to a point near the toe thereof. While depicted as being a hollow channel, the sole channel  104  may be filled or spanned by a plastic, rubber, polymer, or other material to prevent debris from entering the cavity  120 . The sole channel  104  allows for additional deflection of the lower portion of the striking face  118 . By allowing for further deflection of the lower portion of the striking face  118 , increased ball speeds are achieved from ball strikes at lower portions of the striking face  118 , such as ball strikes off the turf. Accordingly, the elastomer element  102  and the sole channel  104  in combination with one another provide for increased flight distance of a golf ball for turf strikes along with more uniform ball speeds across the striking face  118 . 
       FIGS. 2A-2B  depict sections views of a golf club head  200  having an elastomer element  202  and a striking face  218  with a thickened center portion  222 . Golf club head  200  is similar to golf club head  100  discussed above with reference to  FIGS. 1A-1C , except a thickened portion  222  of the striking face  218  is utilized rather than a flange  110 . The thickened portion  222  of the striking face  218  protrudes into the cavity  220 . The front portion  203  of the elastomer element  202  contacts the rear surface  219  of the thickened portion  222 . The rear portion of the elastomer element  202  is received by a recess  209  in a cradle  208 , which is attached to the back portion  212  and substantially similar to the cradle  108  discussed above with reference to  FIGS. 1A-1C . Due the thickened portion  222  of the striking face  218 , the elastomer element  202  may be shorter in length than the elastomer element  102  in  FIGS. 1A-1C . The golf club head  200  also includes a sole channel  204  disposed between a front sole portion  214  and a rear sole portion  216 . The sole channel  204  also provides benefits similar to that of sole channel  104  described in  FIGS. 1A-1C  and may also be filled with or spanned by a material. 
       FIGS. 3A-3B  depict section views of a golf club head  300  having an elastomer element  302  and an adjustment mechanism to adjust the compression of the elastomer element  302 . The golf club head  300  includes a striking face  318  and a back portion  312 , and a cavity  320  is formed between the back portion  312  and the striking face  318 . Similar to the golf club head  100  described above with reference to  FIGS. 1A-1C , a flange  310  is disposed on the rear surface  319  of the striking face  318 , and the flange  310  receives the front portion  303  of the elastomer element  302 . In the example depicted in  FIGS. 3A-3B , the elastomer element  302  has a generally cylindrical shape. In other examples, however, the elastomer element  302  may have a conical, frustoconical, spherical, cuboid, or prism shape. 
     The golf club head  300  also includes an adjustment mechanism. The adjustment mechanism is configured to adjust the compression of the elastomer element  302  against the rear surface  319  of the striking face  318 . In the embodiment depicted in  FIGS. 3A-3B , the adjustment mechanism includes an adjustment receiver  306  and an adjustment driver  330 . The adjustment receiver  306  may be a structure with a through-hole into the cavity  320 , and the adjustment driver  330  may be a threaded element or screw, as depicted. The through-hole of the adjustment receiver  306  includes a threaded interior surface for receiving the threaded element  330 . The adjustment receiver  306  may be formed as part of the forging or casting process of the back portion  312  or may also be machined and tapped following the forging and casting process. The threaded element  330  includes an interface  334 , such as a recess, that contacts or receives a rear portion of the elastomer element  302 . The threaded element  330  also includes a screw drive  332  that is at least partially external to the golf club head  300  such that a golfer can access the screw drive  332 . When the threaded element  330  is turned via screw drive  332 , such as by a screwdriver, Allen wrench, or torque wrench, the threaded element  330  moves further into or out of the cavity  320 . In some examples, the interface  334  that contacts or receives the rear portion of the elastomer element  302  may be lubricated so as to prevent twisting or spinning of the elastomer element  302  when the threaded element  330  is turned. As the threaded element  330  moves further into the cavity  320 , the compression of the elastomer element  302  against the rear surface  319  of the striking face  318  increases, thus altering a performance of the elastomer element  302 . 
     A higher compression of the elastomer element  302  against the rear surface  319  of the striking face  318  further restricts the deflection of the striking face  318 . In turn, further restriction of the deflection causes more uniform ball speeds across the striking face  318 . However, the restriction on deflection also lowers the maximum ball speed from the center of the striking face  318 . By making the compression of the elastomer element  302  adjustable with the adjustment mechanism, the golfer or a golf-club-fitting professional may adjust the compression to fit the particular needs of the golfer. For example, a golfer that desires further maximum distance, but does not need uniform ball speed across the striking face  318 , can reduce the initial set compression of the elastomer element  302  by loosening the threaded element  330 . In contrast, a golfer that desires uniform ball speed across the striking face  318  can tighten the threaded element  330  to increase the initial set compression of the elastomer element  302 . 
     While the adjustment mechanism is depicted as including a threaded element  330  and a threaded through-hole in  FIGS. 3A-3B , other adjustment mechanisms could be used to adjust the compression of the elastomer element  302  against the rear surface  319  of the striking face  318 . For instance, the adjustment mechanism may include a lever where rotation of the lever alters the compression of the elastomer element  302 . The adjustment mechanism may also include a button that may be depressed to directly increase the compression of the elastomer element  302 . Other types of adjustment mechanisms may also be used. 
     The golf club head  300  also includes a sole channel  304  between a front sole portion  314  and a rear sole portion  316 , similar to the sole channel  104  discussed above with reference to  FIGS. 1A-1C . The sole channel  304  also provides benefits similar to that of sole channel  104  and may also be filled with or spanned by a material. 
     The golf club head  300  may also be created or sold as a kit. In the example depicted where the adjustment mechanism is a threaded element  330 , such as a screw, the kit may include a plurality of threaded elements  330 . Each of the threaded elements  330  may have a different weight, such that the golfer can select the desired weight. For example, one golfer may prefer an overall lighter weight for the head of an iron, while another golfer may prefer a heavier weight. The plurality of threaded elements  330  may also each have different weight distributions. For instance, different threaded elements  330  may be configured so as to distribute, as desired, the weight of each threaded element  330  along a length thereof. The plurality of threaded elements  330  may also have differing lengths. By having differing lengths, each threaded elements  330  may have a maximum compression that it can apply to the elastomer element  302 . For instance, a shorter threaded elements  330  may not be able to apply as much force onto the elastomer element  302  as a longer threaded elements  330 , depending on the configuration of the adjustment receiver  306 . The kit may also include a torque wrench for installing the threaded elements  330  into the adjustment receiver  306 . The torque wrench may include preset settings corresponding to different compression or performance levels. 
       FIG. 4A  depicts a perspective view of another example of a golf club head  400 A having an elastomer element  402  and an adjustment mechanism to adjust the compression of the elastomer element  402 .  FIG. 4B  depicts a section view of the golf club head  400 A. The golf club  400 A includes striking face  418  and a back portion  412  with a cavity  420  formed there between. Like the adjustment mechanism in  FIGS. 3A-3B , the adjustment mechanism in golf club head  400 A includes an adjustment receiver  406  and an adjustment driver  430 . In the example depicted, the adjustment receiver  406  is a structure having a threaded through-hole for accepting the adjustment driver  430 , and the adjustment driver  430  is a screw. In some embodiments, the adjustment receiver  406  may be defined by a threaded through-hole through the back portion  412 , without the need for any additional structure. 
     The tip of the screw  430  is in contact with a cradle  408 A that holds a rear portion of the elastomer element  402 . As the screw  430  is turned, the lateral movement of the screw  430  causes the cradle  408 A to move towards or away from the striking face  418 . Accordingly, in some examples, the screw  430  extends substantially orthogonal to the rear surface  419  of the striking face  418 . Because the cradle  408 A holds the rear portion of the elastomer element  402 , movement of the cradle  408 A causes a change in the compression of the elastomer element  402  against the rear surface  419  of the striking face  418 . As such, the compression of the elastomer element  402  may be adjusted by turning the screw  430  via screw drive  432 , similar to manipulation of the threaded element  330  in golf club head  300  depicted in  FIGS. 3A-3B . 
       FIG. 4C  depicts a section view of another example of a golf club  400 C having an elastomer element  402  and an adjustment mechanism to adjust the compression of the elastomer element  402 . The golf club head  400 C is substantially similar to the golf club head  400 A depicted in  FIGS. 4A-4B , except golf club head  400 C includes a larger cradle  408 C having a depth D greater than a depth of a comparatively smaller cradle (e.g., the cradle  408 A of  FIGS. 4A-4B  having a depth d). The larger cradle  408 C encompasses more the elastomer element  402  than a smaller cradle. By encompassing a larger portion of the elastomer element  402 , the cradle  408 C further limits the deformation of the elastomer element  402  upon a strike of a golf ball by golf club head  400 C. Limitation of the deformation of the elastomer element  402  also may limit the potential maximum deflection of the striking face  418 , and therefore may reduce the maximum ball speed for the golf club head  400 C while increasing the uniformity of speeds across the striking face  418 . The larger cradle  408 C does not come into contact with the rear surface  419  of the striking face  418  at maximum deflection thereof. The cradle  408 C itself may be made of the same material as the back portion  412 , such as a steel. The cradle  408 C may also be made from a titanium, a composite, a ceramic, or a variety of other materials. 
     The size of the cradle  408 C may be selected based on the desired ball speed properties. For instance, the cradle  408 C may encompass approximately 25% or more of the volume of the elastomer element  402 , as shown in  FIG. 4C . In other examples, the cradle  408 C may encompass between approximately 25%-50% of the volume of the elastomer element  402 . In yet other examples, the cradle  408 C may encompass approximately 10%-25% or less than approximately 10% of the volume of the elastomer element  402 . In still other examples, the cradle  408 C may encompass more than 50% of the volume of the elastomer element  402 . For the portion of the elastomer element  402  encompassed by the cradle  408 C, substantially the entire perimeter surface of that portion of elastomer element  402  may contact the interior surfaces of the recess  409  of the cradle  408 C. 
     The connection between the cradle  408 C and the adjustment driver  430  can also be seen more clearly in  FIG. 4C . The tip of the adjustment driver  430 , which may be a flat surface, contacts the rear surface  407  of the cradle  408 C. Thus, as the adjustment driver  430  moves into the cavity  420 , the cradle  408 C and the elastomer element  402  are pushed towards the striking face  418 . Conversely, as the adjustment driver  430  is backed out of the cavity  420 , the cradle  408 C maintains contact with the adjustment driver  430  due to the force exerted from the elastomer element  402  resulting from the compression thereof. In some embodiments, the surface of the tip of the screw  430  and/or the rear surface  407  of the cradle  408 C may be lubricated so as to prevent twisting of the cradle  408 C. In other examples, the tip of the adjustment driver  430  may be attached to the cradle  408 C such that the cradle  408 C twists with the turning of the adjustment driver  430 . In such an embodiment, the elastomer element  402  may be substantially cylindrical, conical, spherical, or frustoconical, and the interior  409  of the cradle  408 C may be lubricated to prevent twisting of the elastomer element  402 . In another example, the rear surface  419  of the striking face  418  and/or the front surface of the elastomer element  402  in contact with the rear surface  419  of the striking face  418  may be lubricated so as to allow for spinning of the elastomer element  402  against the rear surface  419  of the striking face  418 . 
     While the golf club heads  400 A and  400 C are depicted with a continuous sole  414  rather than a sole channel like the golf club head  300  of  FIGS. 3A-3B , other embodiments of golf club heads  400 A and  400 C may include a sole channel. In addition, golf club heads  400 A and  400 C may also be sold as kits with a plurality of screws and/or a torque wrench, similar to the kit discussed above for golf club head  300 . An additional back plate may be added to the aft portion of the golf club heads  400 A and  400 C, while still leaving a portion of the screw exposed for adjustment. 
     Simulated results of different types of golf club heads further demonstrate ball speed uniformity across the face of the golf club heads including an elastomer element. Table 1 indicates ball speed retention across the face of a golf club head for several different example golf club heads. Example 1 is a baseline hollow iron having a 2.1 mm face thickness with a sole channel. Example 2 is a hollow iron with a 2.1 mm face with a rigid rod extending from the back portion to the striking face, also including a sole channel. Example 3 is a hollow iron with a striking face having a thick center (6.1 mm) and a thin perimeter (2.1 mm), also having a sole channel. Example 4 is a golf club head having an elastomer element similar to golf club head  100  depicted in  FIGS. 1A-1C . The “Center” row indicates ball speeds resulting from a strike in the center of the golf club head, the “½” Heel” row indicates the loss of ball speed from a strike a half inch from the center of the club head towards the heel, and the “½” Toe” row indicates the loss of ball speed from a strike a half inch from the center of the club head towards the toe. All values in Table 1 are in miles per hour (mph). 
                                             TABLE 1                       Impact    Example    Example    Example    Example            Location    1    2    3    4                                                                Center    134.1    132.8    133.8    133.6            ½″ Heel (drop    −1.0    −0.4    −0.9    −0.7            from center)                           ½″ Toe (drop    −6.9    −6.5    −6.8    −6.7            from center)                        
From the results in Table 1, the golf club head with the elastomer (Example 4) displays a relatively high ball speed from the center of the face, while also providing a reduced loss of ball speed from strikes near the toe or the heel of the golf club.
 
     In addition, as mentioned above, the type of material utilized for any of the elastomer elements discussed herein has an effect on the displacement of the striking face. For instance, an elastomer element with a greater elastic modulus will resist compression and thus deflection of the striking face, leading to lower ball speeds. For example, for a golf club head similar to golf club head  400 A, Table 2 indicates ball speeds achieved from using materials with different elasticity properties. All ball speeds were the result of strikes at the center of the face. 
                             TABLE 2                   Elastic Modulus    Ball Speed        Material    (GPa)    (mph)                                            Material A    0.41    132.2        Material B    0.58    132.2        Material C    4.14    132.0        Material D    41.4    131.0                    
From the results in Table 2, a selection of material for the elastomer element can be used to fine tune the performance of the golf club. Any of the materials listed in Table 2 are acceptable for use in forming an elastomer element to be used in the present technology.
 
     The different types of materials also have effect on the ball speed retention across the striking face. For example, for a golf club head similar to golf club head  400 A, Table 3 indicates ball speeds achieved across the striking face from heel to toe for the different materials used as the elastomer element. The materials referenced in Table 3 are the same materials from Table 2. All speeds in Table 3 are in mph. 
                                         TABLE 3                           ½″ Toe    Center    ½″ Heel            Material    Impact    Impact    Impact                                                            No Elastomer    128.7    132.2    129.4            Element                        Material A    128.7    132.2    129.4            (0.41 GPa)                        Material C    128.7    132.0    129.3            (4.1 GPa)                        Material D    127.9    131.0    128.7            (41 GPa)                        
From the results in Table 3, materials having a higher elastic modulus provide for better ball speed retention across the striking face, but lose maximum ball speed for impacts at the center of the face. For some applications, a range of elastic moduli for the elastomer element from about 4 to about 15 GPa may be used. In other applications, a range of elastic moduli for the elastomer element from about 1 to about 40 or about 50 GPa may be used.
 
     As mentioned above with reference to  FIGS. 4A-4C , the size of the cradle may also have an impact on the ball speed. For a smaller cradle, such as cradle  408 A in  FIGS. 4A-4B , and an elastomer element made of a 13 GPa material, a loss of about 0.2 mph is observed for a center impact as compared to the same club with no elastomer element. For a larger cradle that is about 5 mm deeper, such as cradle  408 C in  FIG. 4C , and an elastomer element also made of a 13 GPa material, a loss of about 0.4 mph is observed for a center impact as compared to the same club with no elastomer element. For the same larger cradle and an elastomer element made of a 0.4 GPa material, a loss of only about 0.2 mph is observed for a center impact as compared to the same club with no elastomer element. 
     San Diego Plastics, Inc. of National City, Calif. offers several plastics having elastic moduli ranging from 2.6 GPa to 13 GPa that would all be acceptable for use. The plastics also have yield strengths that are also acceptable for use in the golf club heads discussed herein. Table 4 lists several materials offered by San Diego Plastics and their respective elastic modulus and yield strength values. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Tecapeek  
               
               
                   
                   
                 Tecaform  
                   
                   
                 30% Carbon  
               
               
                   
                 ABS  
                 Acetal  
                 PVC  
                 Tecapeek  
                 Fiber 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Thermoplastic  
                 2.8  
                 2.6  
                 2.8  
                 3.6  
                 13  
               
               
                 Elastic  
                   
                   
                   
                   
                   
               
               
                 Modulus (GPa)  
                   
                   
                   
                   
                   
               
               
                 Thermoplastic  
                 0.077  
                 0.031  
                 0.088  
                 0.118  
                 0.240  
               
               
                 Compressive  
                   
                   
                   
                   
                   
               
               
                 Yield Strength  
                   
                   
                   
                   
                   
               
               
                 (GPa) 
               
               
                   
               
            
           
         
       
     
     The inclusion of an elastomer element also provide benefits in durability for the club face by reducing stress values displayed by the striking face upon impact with a golf ball.  FIG. 5A  depicts a stress contour diagram for a golf club head  500 A without an elastomer element, and  FIG. 5B  depicts a stress contour diagram for a golf club head  500 B with an elastomer element. In the golf club head  500 A, the von Mises stress at the center of the face  502 A is about 68% of the maximum von Mises stress, which occurs at the bottom face edge  504 A. Without an elastomer element, the von Mises stress levels are high and indicate that the club face may be susceptible to failure and/or early deterioration. In the golf club  500 B, for an elastomer element having an elastic modulus of 0.41 GPa, the von Mises stress for the face near the edge of the elastomer element  502 B is reduced by about 16% and the maximum von Mises stress occurring at the bottom face edge  504 B is reduced by about 18%. These von Mises stresses are still relatively high, but are significantly reduced from those of the golf club head  500 A. For a golf club head  500 B with an elastomer element having an elastic modulus of about 13 GPa, the von Mises stress for the face near the edge of the elastomer element  502 B is reduced by about 50% and the maximum von Mises stress occurring at the bottom face edge  504 B is reduced by about 56%. Such von Mises stress values are lower and are indicative of a more durable golf club head that may be less likely to fail. 
       FIGS. 6A-6E  depict a golf club head  600  having an elastomer element  602 .  FIG. 6A  depicts a front view of the golf club head  600 .  FIG. 6B  depicts a toe view of the golf club head  600  of  FIG. 6A .  FIG. 6C  depicts a section view A-A of the golf club head  600  of  FIG. 6A .  FIG. 6D  depicts a perspective view of the golf club head  600  of  FIG. 6A  oriented perpendicular to the striking face  618 .  FIG. 6E  depicts a perspective view of the golf club head  600  of  FIG. 6A  oriented perpendicular to the striking face  618  including the supported region  642 . The golf club head  600  includes a striking face  618  configured to strike a ball, a sole  605  located at the bottom of the golf club head  600 , and a back portion  612 . 
     As illustrated in  FIGS. 6A and 6B , the golf club head  600  includes a coordinate system centered at the center of gravity (CG) of the golf club head  600 . The coordinate system includes a y-axis which extends vertically, perpendicular to a ground plane when the golf club head  600  is in an address position at prescribed lie and loft a. The coordinate system includes an x-axis, perpendicular to the y-axis, parallel to the striking face  618 , and extending towards the heel of the golf club head  600 . The coordinate system includes a z-axis, perpendicular to the y-axis and x-axis and extending through the striking face  618 . The golf club head  600  has a rotational moment of inertia about the y-axis (MOI-Y), a value which represents the golf club head&#39;s resistance to angular acceleration about the y-axis. 
     An elastomer element  602  is disposed between the striking face  618  and the back portion  612 . The striking face  618  includes a rear surface  619 . The front portion  603  of the elastomer element  602  contacts the rear surface  619  of the striking face  618 . As illustrated in  FIGS. 6C and 6E , the striking face  618  includes a supported region  642 , the portion of the rear surface  619  supported by the elastomer element  602 , which is defined as the area inside the supported region perimeter  640  defined by the outer extent of the front portion  603  of the elastomer element  602  in contact with the rear surface  619  of the striking face  618 . The supported region  642  is illustrated with hatching in  FIG. 6E . The supported region  642  wouldn&#39;t normally be visible from the front of the golf club head  600  but was added for illustrative purposes. 
     The striking face  618  includes a striking face area  652 , which is defined as the area inside the striking face perimeter  650  as illustrated in  FIG. 6D . As illustrated in  FIG. 6C , the striking face perimeter is delineated by an upper limit  654  and a lower limit  656 . The upper limit  654  is located at the intersection of the substantially flat rear surface  619  and the upper radius  655  which extends to the top line of the golf club head  600 . The lower limit  656  is located at the intersection of the substantially flat rear surface  619  and the lower radius  657  which extends to the sole  605  of the golf club head  600 . The striking face perimeter is similarly delineated  658  (as illustrated in  FIG. 6D ) at the toe of the golf club head  600  (not illustrated in cross section). The heel portion of the striking face perimeter is defined by a plane  659  extending parallel to the y-axis and the x-axis offset 1 millimeter (mm) towards the heel from the heel-most extent of the scorelines  660  formed in the striking face  618 . The striking face area  652  is illustrated with hatching in  FIG. 6D . The limits  654 ,  656  of the striking face perimeter have been projected onto the striking face  618  in  FIG. 6D  for ease of illustration and understanding. 
     A plurality of golf club heads much like golf club head  600  described herein can be included in a set, each golf club head having a different loft a. Each golf club head can also have additional varying characteristics which may include, for example, MOI-Y, Striking Face Area, Area of Supported Region, and the Unsupported Face Percentage. The Unsupported Face Percentage is calculated by dividing the Area of Supported Region by the Striking Face Area and multiplying by 100% and subtracting it from 100%. An example of one set of iron type golf club heads is included in Table 5 below. The set in Table 5 includes the following lofts:  21 ,  24 ,  27 , and  30 . Other sets may include a greater number of golf club heads and/or a wider range of loft a values, or a smaller number of golf club heads and/or a smaller range of loft a values. Additionally, a set may include one or more golf club heads which include an elastomer element and one or more golf club heads which do not include an elastomer element. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                 Striking  
                 Area of  
                 Unsupported  
               
               
                   
                   
                 Face  
                 Supported  
                 Face  
               
               
                 Loft of Iron  
                 MOI-Y  
                 Area  
                 Region  
                 Percentage  
               
               
                 (Degrees)  
                 (kg*mm 2 )  
                 (mm 2 )  
                 (mm 2 )  
                 (%) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 21  
                 270  
                 2809  
                 74  
                 97.37  
               
               
                 24  
                 272  
                 2790  
                 74  
                 97.35  
               
               
                 27  
                 276  
                 2777  
                 74  
                 97.34  
               
               
                 30  
                 278  
                 2742  
                 74  
                 97.30 
               
               
                   
               
            
           
         
       
     
     An example of an additional embodiment of set of iron type golf club heads is included in Table 6 below. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                   
                   
                 Striking  
                 Area of  
                 Unsupported  
               
               
                   
                   
                 Face  
                 Supported  
                 Face  
               
               
                 Loft of Iron  
                 MOI-Y  
                 Area  
                 Region  
                 Percentage  
               
               
                 (Degrees)  
                 (kg*mm 2 )  
                 (mm 2 )  
                 (mm 2 )  
                 (%) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 21  
                 272  
                 2897  
                 74  
                 97.45  
               
               
                 24  
                 278  
                 2890  
                 74  
                 97.44  
               
               
                 27  
                 289  
                 2878  
                 74  
                 97.43  
               
               
                 30  
                 294  
                 2803  
                 74  
                 97.36 
               
               
                   
               
            
           
         
       
     
     If all other characteristics are held constant, a larger the MOI-Y value increases the ball speed of off-center hits. For clubs with a smaller MOI-Y, the decrease in off-center ball speed can be mitigated with a greater unsupported face percentage. By supporting a smaller percentage of the face, more of the face is able to flex during impact, increasing off-center ball speed. Thus, for the inventive golf club set described in Table 5 above, the MOI-Y increases through the set as loft a increases and the unsupported face percentage decreases through the set as loft a increases. This relationship creates consistent off-center ball speeds through a set of golf clubs. 
     A set of golf clubs can include a first golf club head with a loft greater than or equal to 20 degrees and less than or equal to 24 degrees and a second golf club head with a loft greater than or equal to 28 degrees and less than or equal to 32 degrees. In one embodiment, the set can be configured so that the first golf club head has a larger unsupported face percentage than the second golf club head and the first golf club head has a lower MOI-Y than the second golf club head. 
     More particular characteristics of embodiments described herein are described below. In some embodiments, the area of the supported region can be greater than 30 millimeters 2 . In some embodiments, the area of the supported region can be greater than 40 millimeters 2 . In some embodiments, the area of the supported region can be greater than 60 millimeters 2 . In some embodiments, the area of the supported region can be greater than 65 millimeters 2 . In some embodiments, the area of the supported region can be greater than 70 millimeters 2 . In some embodiments, the area of the supported region can be greater than 73 millimeters 2 . 
     In some embodiments, the area of the supported region can be less than 140 millimeters 2 . In some embodiments, the area of the supported region can be less than 130 millimeters 2 . In some embodiments, the area of the supported region can be less than 120 millimeters 2 . In some embodiments, the area of the supported region can be less than 110 millimeters 2 . In some embodiments, the area of the supported region can be less than 100 millimeters 2 . In some embodiments, the area of the supported region can be less than 90 millimeters 2 . In some embodiments, the area of the supported region can be less than 85 millimeters 2 . In some embodiments, the area of the supported region can be less than 80 millimeters 2 . In some embodiments, the area of the supported region can be less than 75 millimeters 2 . 
     In some embodiments, the unsupported face percentage is greater than 70%. In some embodiments, the unsupported face percentage is greater than 75%. In some embodiments, the unsupported face percentage is greater than 80%. In some embodiments, the unsupported face percentage is greater than 85%. In some embodiments, the unsupported face percentage is greater than 90%. In some embodiments, the unsupported face percentage is greater than 95%. In some embodiments, the unsupported face percentage is greater than 96%. In some embodiments, the unsupported face percentage is greater than 97%. 
     In some embodiments, the unsupported face percentage is less than 99.75%. In some embodiments, the unsupported face percentage is less than 99.50%. In some embodiments, the unsupported face percentage is less than 99.25%. In some embodiments, the unsupported face percentage is less than 99.00%. In some embodiments, the unsupported face percentage is less than 98.75%. In some embodiments, the unsupported face percentage is less than 98.50%. In some embodiments, the unsupported face percentage is less than 98.25%. In some embodiments, the unsupported face percentage is less than 98.00%. In some embodiments, the unsupported face percentage is less than 97.75%. In some embodiments, the unsupported face percentage is less than 97.50%. In some embodiments, the unsupported face percentage is less than 97.25%. In some embodiments, the unsupported face percentage is less than 97.00%. 
       FIGS. 7A-10  depict a golf club head  700  having an elastomer element  702 .  FIG. 7A  depicts a perspective view of the golf club head  700 .  FIG. 7B  depicts an additional perspective view of the golf club head  700  of  FIG. 7A .  FIG. 7C  depicts a rear view of the golf club head  700  of  FIG. 7A .  FIG. 8A  depicts a section view B-B of the golf club head  700  of  FIG. 7C .  FIG. 8B  depicts a section view C-C of the golf club head  700  of  FIG. 7C .  FIG. 8C  depicts a section view D-D of the golf club head  700  of  FIG. 7C .  FIG. 9A  depicts an additional section view of the front of the golf club head  700  of  FIG. 7A  missing the striking face.  FIG. 9B  depicts the section view from  FIG. 9A  with the elastomer element removed.  FIG. 10 . Depicts a perspective view of the golf club head  700  of  FIG. 7A  oriented perpendicular to the striking face  718  including the supported region  742 . Please note that the golf club head  700  illustrated in  FIGS. 7A-10  is an iron-type cavity back golf club but the inventions described herein are applicable to other types of golf club heads as well. 
     The golf club head  700  includes a deformable member  702  disposed between the striking face  718  and the back portion  712 . In one embodiment, the deformable member  702  is formed from an elastomer. The front portion  703  of the elastomer element  702  contacts the rear surface  719  of the striking face  718 . The striking face  718  includes a supported region  742 , the portion of the rear surface  719  supported by the elastomer element  702 , which is defined as the area inside the supported region perimeter  740  defined by the outer extent of the front portion  703  of the elastomer element  702  in contact with the rear surface  719  of the striking face  718 . The supported region  742  wouldn&#39;t normally be visible from the front of the golf club head  700  but was added in  FIG. 10  for illustrative purposes. 
     The golf club head  700  illustrated in  FIGS. 7A-10  is a cavity back construction and includes a periphery portion  701  surrounding and extending rearward from the striking face  718 . The periphery portion  701  includes the sole  705 , the toe  706 , and the topline  707 . The periphery portion  701  can also include a weight pad  710 . The golf club head  700  also includes a back portion  712  configured to support the elastomer element  702 . 
     The back portion  712  includes a cantilever support arm  762  affixed to the periphery portion  701 . The support arm  762  can include a cradle  708  configured to hold the elastomer element  702  in place. The cradle  708  can include a lip  709  configured to locate the elastomer element  702  on the cradle  708  and relative to the striking face  718 . The lip  709  can surround a portion of the elastomer element  702 . Additionally, an adhesive can be used between the elastomer element  702  and the cradle  708  to secure the elastomer element  702  to the cradle  708 . 
     The support arm  762  extends from the weight pad  710  located at the intersection of the sole  705  and the toe  706  of the periphery portion  701  towards the supported region  742 . The support arm  762  is oriented substantially parallel to the rear surface  719  of the striking face  718 . The support arm  762  can include a rib  764  to increase the stiffness of the support arm  762 . The rib  764  can extend rearwards from the support arm  762  substantially perpendicularly to the rear surface  719  of the striking face  718 . One benefit of a cantilever support arm  762  is it provides a lower CG height than an alternative beam design, such as the embodiment illustrated in  FIG. 4A , which supported at both ends by the periphery portion. 
     In order to provide a low CG height the support arm  762  is cantilevered which means it is only affixed to the periphery portion  701  at one end of the support arm  762 . The support arm is designed such that the distance H between the highest portion of the support arm  762  and the ground plane GP when the golf club head  700  is in an address position, as illustrated in  FIG. 8C , is minimized, while locating the elastomer element  702  in the optimal position. In one embodiment, H is less than or equal to 50 mm. In an additional embodiment, H is less than 45 mm. In an additional embodiment, H is less than or equal to 40 mm. In an additional embodiment, H is less than or equal to 35 mm. In an additional embodiment, H is less than or equal to 30 mm. In an additional embodiment, H is less than or equal to 29 mm. In an additional embodiment, H is less than or equal to 28 mm. 
     In one embodiment, the golf club head  700  can have a CG height CGH of less than or equal to 25 mm. In an additional embodiment, the golf club head  700  can have a CG height CGH of less than or equal to 24 mm. In an additional embodiment, the golf club head  700  can have a CG height CGH of less than or equal to 23 mm. In an additional embodiment, the golf club head  700  can have a CG height CGH of less than or equal to 22 mm. In an additional embodiment, the golf club head  700  can have a CG height CGH of less than or equal to 21 mm. In an additional embodiment, the golf club head  700  can have a CG height CGH of less than or equal to 20 mm. In an additional embodiment, the golf club head  700  can have a CG height CGH of less than or equal to 19 mm. In an additional embodiment, the golf club head  700  can have a CG height CGH of less than or equal to 18 mm. 
     Another advantage to the illustrated support arm  762  is it provides a high MOI-Y due to its orientation. By concentrating mass at the heel end and toe end of the golf club head  700  the MOI-Y can be increased. The support arm  762  is angled to concentrate much of its mass near the toe  706 , increasing MOI-Y compared with a back portion located more centrally on the golf club head  700 . In one embodiment, the MOI-Y of the golf club head  700  is greater than or equal to 200 kg-mm 2 . In an additional embodiment, the MOI-Y of the golf club head  700  is greater than or equal to 210 kg-mm 2 . In an additional embodiment, the MOI-Y of the golf club head  700  is greater than or equal to 220 kg-mm 2 . In an additional embodiment, the MOI-Y of the golf club head  700  is greater than or equal to 230 kg-mm 2 . In an additional embodiment, the MOI-Y of the golf club head  700  is greater than or equal to 240 kg-mm 2 . In an additional embodiment, the MOI-Y of the golf club head  700  is greater than or equal to 250 kg-mm 2 . In an additional embodiment, the MOI-Y of the golf club head  700  is greater than or equal to 260 kg-mm 2 . In an additional embodiment, the MOI-Y of the golf club head  700  is greater than or equal to 270 kg-mm 2 . 
     The support arm  762  can include an arm centerline CL, as illustrated in  FIG. 8A , which is oriented parallel to the rear surface  719  of the striking face  718  and extends along the center of the support arm  762  from the periphery portion  701  towards the supported region  742 . The angle α is measured between the ground plane GP and the centerline CL. In one embodiment, the angle α is greater than or equal to 5 degrees and less than or equal to 45 degrees. In an additional embodiment, the angle α is greater than or equal to 10 degrees and less than or equal to 40 degrees. In an additional embodiment, the angle α is greater than or equal to 15 degrees and less than or equal to 35 degrees. In an additional embodiment, the angle α is greater than or equal to 20 degrees and less than or equal to 30 degrees. In an additional embodiment, the angle α is greater than or equal to 23 degrees and less than or equal to 28 degrees. 
     The support arm  762  can have an arm width AW measured perpendicularly to the arm centerline CL and parallel to the rear surface  719  of the striking face  718 . The arm width AW can vary along the length of the support arm  762 . In one embodiment the arm width of at least one portion of the support arm is greater than or equal to 6 mm. In an additional embodiment the arm width of at least one portion of the support arm is greater than or equal to 8 mm. In an additional embodiment the arm width of at least one portion of the support arm is greater than or equal to 10 mm. 
     The support arm  762  can have an arm thickness AT measured perpendicular to the rear surface  719  of the striking face  718 . The arm thickness AT can vary along the length of the support arm  762 . In one embodiment the arm thickness AT of at least one portion of the support arm is greater than or equal to 2 mm. In an additional embodiment the arm thickness AT of at least one portion of the support arm is greater than or equal to 3 mm. In an additional embodiment the arm thickness AT of at least one portion of the support arm is greater than or equal to 4 mm. In an additional embodiment the arm thickness AT of at least one portion of the support arm is greater than or equal to 5 mm. In an additional embodiment the arm thickness AT of at least one portion of the support arm is greater than or equal to 6 mm. 
     The rib  764  of the support arm  762  can have a rib width RW measured perpendicularly to the arm centerline CL and parallel to the rear surface  719  of the striking face  718 . The rib width RW can vary along the length of the rib. In one embodiment, the rib width RW of at least a portion of the rib is greater than or equal to 1 mm. In an additional embodiment, the rib width RW of at least a portion of the rib is greater than or equal to 2 mm. In an additional embodiment, the rib width RW of at least a portion of the rib is greater than or equal to 3 mm. In an additional embodiment, the rib width RW of at least a portion of the rib is greater than or equal to 4 mm. 
     The rib  764  of the support arm  762  can have a rib thickness RT measured perpendicular to the rear surface  719  of the striking face  718 . The rib thickness RT can vary along the length of the rib. In one embodiment, the rib thickness RT of at least a portion of the rib is greater than or equal to 2 mm. In an additional embodiment, the rib thickness RT of at least a portion of the rib is greater than or equal to 3 mm. In an additional embodiment, the rib thickness RT of at least a portion of the rib is greater than or equal to 4 mm. In an additional embodiment, the rib thickness RT of at least a portion of the rib is greater than or equal to 5 mm. In an additional embodiment, the rib thickness RT of at least a portion of the rib is greater than or equal to 6 mm. 
     The supported region  742 , as illustrated in  FIG. 10 , is specifically located on the rear surface  719  of the striking face  718 . The striking face heel reference plane  759  extends parallel to the y-axis and the x-axis and is offset 1 mm towards the heel from the heel-most extent of the scorelines  760  formed in the striking face  718 . The geometric center  743  of the supported region  742  is located a supported region offset length SROL toeward from the striking face heel reference plane  759  measured parallel to the ground plane GP and parallel to the striking face  718  with the golf club head  700  in an address position. In one embodiment, the supported region offset length SROL is greater than or equal to 20 mm. In an additional embodiment, the supported region offset length SROL is greater than or equal to 22 mm. In an additional embodiment, the supported region offset length SROL is greater than or equal to 24 mm. In an additional embodiment, the supported region offset length SROL is greater than or equal to 26 mm. In an additional embodiment, the supported region offset length SROL is greater than or equal to 27 mm. In an additional embodiment, the supported region offset length SROL is greater than or equal to 28 mm. 
     The striking face length SFL is measured from the striking face heel reference plane  759  to the toe-most extent of the striking face  718 , measured parallel to the ground plane GP and parallel to the striking face  718  with the golf club head  700  in an address position. In one embodiment, the striking face length SFL is greater than or equal to 60 mm. In an additional embodiment, the striking face length SFL is greater than or equal to 65 mm. In an additional embodiment, the striking face length SFL is greater than or equal to 70 mm. In an additional embodiment, the striking face length SFL is greater than or equal to 71 mm. In an additional embodiment, the striking face length SFL is greater than or equal to 72 mm. In an additional embodiment, the striking face length SFL is greater than or equal to 73 mm. In an additional embodiment, the striking face length SFL is greater than or equal to 74 mm. 
     In one embodiment, the supported region offset ratio, defined as the supported region offset length SROL divided by the striking face length SFL multiplied by 100%, is greater than or equal to 40%. In an additional embodiment, the supported region offset ratio is greater than or equal to 41%. In an additional embodiment, the supported region offset ratio is greater than or equal to 42%. In an additional embodiment, the supported region offset ratio is greater than or equal to 43%. In an additional embodiment, the supported region offset ratio is greater than or equal to 44%. In an additional embodiment, the supported region offset ratio is greater than or equal to 45%. In an additional embodiment, the supported region offset ratio is greater than or equal to 46%. In an additional embodiment, the supported region offset ratio is greater than or equal to 47%. In an additional embodiment, the supported region offset ratio is greater than or equal to 48%. In an additional embodiment, the supported region offset ratio is greater than or equal to 49%. In an additional embodiment, the supported region offset ratio is greater than or equal to 50%. In an additional embodiment, the supported region offset ratio is greater than or equal to 51%. 
     An additional benefit of incorporating a supported region  742  is the ability to utilize a thin striking face. In the illustrated embodiments, the striking face  718  has a constant thickness. In other embodiments, the striking face may have a variable thickness. In one embodiment, the thickness of the striking face is less than or equal to 2.5 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 2.4 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 2.3 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 2.2 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 2.1 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 2.0 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 1.9 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 1.8 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 1.7 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 1.6 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 1.5 mm. In an additional embodiment, the thickness of the striking face is less than or equal to 1.4 mm. 
       FIGS. 11A-11D  depict the golf club head  700  of  FIG. 7A  having additional embodiments of an elastomer element  702 .  FIG. 11A  illustrates a cross sectional view of the golf club head  700  including an additional embodiment of an elastomer element  702 . The elastomer element  702  of  FIG. 11A  is circular similar to the embodiment illustrated in  FIG. 7A . The front portion  703  of the elastomer element  702 , which abuts the rear surface  719  of the striking face  718 , has a front diameter FD and the rear portion  744 , which abuts the cradle  708 , has a rear diameter RD. The front diameter FD is substantially similar or equal to the rear diameter RD of the elastomer element  702  illustrated in  FIG. 11A . 
       FIG. 11B  illustrates a cross sectional view of the golf club head  700  including an additional embodiment of an elastomer element  702 . The elastomer element  702  of  FIG. 11B  is circular. The front diameter FD is greater than rear diameter RD of the elastomer element  702  illustrated in  FIG. 11B . The rear portion  744  of the elastomer element  702  in contact with the cradle  708  has a rear support region  747 , which has an area. 
       FIG. 11C  illustrates a cross sectional view of the golf club head  700  including an additional embodiment of an elastomer element  702 . The elastomer element  702  of  FIG. 11C  is circular. The front diameter FD is greater than rear diameter RD of the elastomer element  702  illustrated in  FIG. 11C . 
       FIG. 11D  illustrates a cross sectional view of the golf club head  700  including an additional embodiment of an elastomer element  702 . The elastomer element  702  of  FIG. 11D  is circular. The front diameter FD is greater than rear diameter RD of the elastomer element  702  illustrated in  FIG. 11D . Additionally, the rear portion  744  has a constant diameter region  745  aft of the tapered region  746  extending towards the striking face  718 . In one embodiment, the rear diameter RD is approximately 12.5 mm and the front diameter FD is approximately 18.5 mm. 
     The enlarged front portion  703  and thus enlarged supported region  742  offered by the embodiments of the elastomer elements  702  illustrated in  FIGS. 11B, 11C, and 11D  offer advantages. These advantages include more consistent off-center ball speeds, reduced sound energy, particularly above 3800 Hz. 
     In one embodiment, the area of the supported region can be greater than 75 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 100 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 125 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 150 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 175 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 200 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 225 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 250 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 255 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 260 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 50 millimeters 2  and less than 1000 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 100 millimeters 2  and less than 1000 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 150 millimeters 2  and less than 1000 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 200 millimeters 2  and less than 1000 millimeters 2 . In an additional embodiment, the area of the supported region can be greater than 250 millimeters 2  and less than 1000 millimeters 2 . 
     In one embodiment, the ratio of the front diameter FD divided by the rear diameter RD is greater than 1.2. In an additional embodiment, the ratio of the front diameter FD divided by the rear diameter RD is greater than 1.4. In an additional embodiment, the ratio of the front diameter FD divided by the rear diameter RD is greater than 1.6. In an additional embodiment, the ratio of the front diameter FD divided by the rear diameter RD is greater than 1.8. In an additional embodiment, the ratio of the front diameter FD divided by the rear diameter RD is greater than 2.0. In an additional embodiment, the ratio of the front diameter FD divided by the rear diameter RD is greater than 3.0. In an additional embodiment, the ratio of the front diameter FD divided by the rear diameter RD is greater than 4.0. 
     In one embodiment, the area of the supported region  742  is greater than the area of the rear support region  747 . In one embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 1.2. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 1.4. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 1.6. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 1.8. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 2.0. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 2.5. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 3.0. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 3.5. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 4.0. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 5.0. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 6.0. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 7.0. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 8.0. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 9.0. In an additional embodiment, the ratio of the supported region  742  divided by the area of the rear supported region  747  is greater than 10.0. 
     The contact energy absorption factor is defined as the ratio of the front diameter FD divided by the diameter of a golf ball, which is approximately 42.75 mm. In one embodiment, the contact energy absorption factor is greater than 0.1. In an additional embodiment, the contact energy absorption factor is greater than 0.2. In an additional embodiment, the contact energy absorption factor is greater than 0.3. In an additional embodiment, the contact energy absorption factor is greater than 0.4. In an additional embodiment, the contact energy absorption factor is greater than 0.5. In an additional embodiment, the contact energy absorption factor is greater than 0.6. In an additional embodiment, the contact energy absorption factor is greater than 0.7. In an additional embodiment, the contact energy absorption factor is greater than 0.8. In an additional embodiment, the contact energy absorption factor is greater than 0.9. In an additional embodiment, the contact energy absorption factor is greater than 1.0. In an additional embodiment, the contact energy absorption factor is less than 0.2. In an additional embodiment, the contact energy absorption factor is less than 0.3. In an additional embodiment, the contact energy absorption factor is less than 0.4. In an additional embodiment, the contact energy absorption factor is less than 0.5. In an additional embodiment, the contact energy absorption factor is less than 0.6. In an additional embodiment, the contact energy absorption factor is less than 0.7. In an additional embodiment, the contact energy absorption factor is less than 0.8. In an additional embodiment, the contact energy absorption factor is less than 0.9. In an additional embodiment, the contact energy absorption factor is less than 1.0. 
     In additional embodiments, the elastomer elements  702  may not be circular. They may have additional shapes which may include square, rectangular, octagonal, etc. 
     Identical golf club heads with different elastomer elements were subjected to acoustic testing to determine the effectiveness of different embodiments of elastomer elements. The testing was performed with each club head striking a Titleist ProV1 golf ball with a club head speed at impact of approximately 95 miles per hour. The acoustic qualities of the embodiments illustrated in  FIGS. 11A and 11D  were recorded when each golf club head struck a golf ball.  FIGS. 12A and 12B  reflect the recording of the golf club head utilizing the cylindrical elastomer element embodiment illustrated in  FIG. 11A  striking a golf ball and  FIGS. 13A and 13B  reflect the recording of the golf club head utilizing the tapered elastomer element embodiment illustrated in  FIG. 11D  striking a golf ball.  FIG. 12A  illustrates the periodogram power spectral density estimate of the  FIG. 11A  cylindrical embodiment.  FIG. 12B  illustrates the sound power estimate of the  FIG. 11A  cylindrical embodiment.  FIG. 13A  illustrates the periodogram power spectral density estimate of the  FIG. 11D  tapered embodiment.  FIG. 13B  illustrates the sound power estimate of the  FIG. 11D  tapered embodiment. 
     As illustrated in  FIGS. 12A and 12B , the dominant frequency for the cylindrical elastomer element  702  of  FIG. 11A  is 4,279.7 HZ. As illustrated in  FIGS. 13A and 13B , the dominant frequency for the tapered elastomer element  702  of  FIG. 11D  is 4317.4 Hz. Generally, when an iron type golf club head strikes a golf ball, sound frequencies produced between approximately 1,000 Hz and 3,800 Hz are produced by golf club and golf ball interaction and golf ball resonances while sound frequencies above approximately 3,800 Hz are produced solely by the golf club head. Thus, the first sound power peak in the sound power estimate graphs of  FIGS. 12B and 13B  correlates primarily to the golf ball and the subsequent sound power peak correlates to the vibration of the striking face of the golf club head. As illustrated in  FIGS. 12B and 13B  the peak sound power estimate below 3,800 Hz, corresponding to the golf ball, is approximately 1.00×10 −3  watts. As illustrated in  FIG. 12B , the sound power generated by the golf club head utilizing the cylindrical elastomer element embodiment illustrated in  FIG. 11A  peaks at approximately 1.40×10 −3  watts. As illustrated in  FIG. 13B , the sound power generated by the golf club head utilizing the tapered elastomer element embodiment illustrated in  FIG. 11D  peaks at approximately 1.04×10 −3  watts. Sound power levels correlate directly with the loudness of the sound produced by the golf club striking a golf ball. Therefore, it is evident that the sound produced by the golf club head utilizing the cylindrical elastomer element embodiment illustrated in  FIG. 11A  is significantly less loud than the golf club head utilizing the tapered elastomer element embodiment illustrated in  FIG. 11D . 
     Additionally, the sound power generated by the golf club head utilizing the cylindrical elastomer element embodiment illustrated in  FIG. 11A  divided by the sound power generated by the golf ball is approximately 1.40. The sound power generated by the golf club head utilizing the cylindrical elastomer element embodiment illustrated in  FIG. 11D  divided by the sound power generated by the golf ball is approximately 1.04. In some embodiments, it is preferable to have the sound power generated by the golf club head divided by the sound power generated by the golf ball to be less than 1.50. In some embodiments, it is preferable to have the sound power generated by the golf club head divided by the sound power generated by the golf ball to be less than 1.40. In some embodiments, it is preferable to have the sound power generated by the golf club head divided by the sound power generated by the golf ball to be less than 1.30. In some embodiments, it is preferable to have the sound power generated by the golf club head divided by the sound power generated by the golf ball to be less than 1.20. In some embodiments, it is preferable to have the sound power generated by the golf club head divided by the sound power generated by the golf ball to be less than 1.10. In some embodiments, it is preferable to have the sound power generated by the golf club head divided by the sound power generated by the golf ball to be less than 1.00. 
       FIGS. 14A-L  depict additional embodiments of an elastomer element  702 , which can also be referred to as a deformable member. These embodiments are designed with variable compressive stiffness, spring rate, or flexural modulus. This can be achieved through various geometries as well as combinations of various co-molded materials of different durometers. 
       FIG. 14A  illustrates a cross sectional view of an elastomer element  702  having a larger rear portion  744  than front portion  702 . The front portion  702  and rear portion  744  are substantially planar.  FIG. 14B  illustrates a cross sectional view of an elastomer element  702  having a larger rear portion  744  than front portion  702 . The rear portion  744  is substantially planar and the front portion  702  is hemispherical.  FIG. 14C  illustrates a cross sectional view of an elastomer element  702  having a larger rear portion  744  than front portion  702 . The elastomer element  702  includes a front constant diameter region  746  and a rear constant diameter region  745 , where the rear constant diameter region  746  has a larger diameter than the front constant diameter region  745 .  FIG. 14D  illustrates a cross sectional view of an elastomer element  702  similar to that of  FIG. 14A  but includes a first material  770  and a second material  780 . In one embodiment, the first material  770  can be stiffer than the second material  780 . In an additional embodiment, the second material  780  can be stiffer than the first material  770 .  FIG. 14E  illustrates a cross sectional view of an elastomer element  702  similar to that of  FIG. 14B  but includes a first material  770  and a second material  780 .  FIG. 14F  illustrates a cross sectional view of an elastomer element  702  similar to that of  FIG. 14C  but includes a first material  770  and a second material  780 . 
       FIG. 14G  illustrates a cross sectional view of an elastomer element  702  similar to that of  FIG. 14A  but the center of the front portion  703  is offset from a center of the rear portion  744 . The offset can be towards the topline, towards, the sole, towards the toe, towards the heel, or any combination thereof.  FIG. 14H  illustrates a cross sectional view of an elastomer element  702  similar to that of  FIG. 14B  but the center of the front portion  703  is offset from a center of the rear portion  744 .  FIG. 14I  illustrates a cross sectional view of an elastomer element  702  similar to that of  FIG. 14C  but the center of the front portion  703  is offset from a center of the rear portion  744 .  FIG. 14J  illustrates a cross sectional view of an elastomer element  702  which necks down in diameter between the front portion  703  and the rear portion  744 .  FIG. 14K  illustrates a cross sectional view of an elastomer element  702  which necks down in diameter between the front portion  703  and the rear portion  744 .  FIG. 14L  illustrates a cross sectional view of an elastomer element  702  similar to that of  FIG. 14J  but includes a first material  770  and a second material  780 . 
     Any of these embodiments of elastomer element  702  described herein can be flipped, such that the rear portion  744  abuts the rear surface of the striking face rather than the front portion  704 . Additionally, the embodiments illustrated in  FIGS. 14A-14L  are circular when viewed from a front view in a preferred embodiment. In other embodiments, the elastomer elements may comprise different shapes. In some embodiments, the flexural modulus of the first material can be greater than the flexural modulus of the second material. 
       FIGS. 15A-15D  depict a golf club head  800  having an elastomer element  702 .  FIG. 15A  depicts a rear view of the golf club head  800 .  FIG. 15B  depicts a perspective view of the golf club head  800  of  FIG. 15A .  FIG. 15C  depicts an additional perspective view of the golf club head  800  of  FIG. 15A .  FIG. 15D  depicts a section view E-E of the golf club head  800  of  FIG. 15A .  FIG. 16  depicts the section view E-E of the golf club head  800  of  FIG. 15D  without the adjustment driver  830  and elastomer element  702  installed.  FIG. 17A  depicts a perspective view of the adjustment driver  830  and elastomer element  702  of the golf club head  800  of  FIG. 15A .  FIG. 17B  depicts an additional perspective view of the adjustment driver  830  and elastomer element  702  of the golf club head  800  of  FIG. 15A .  FIG. 17C  depicts a side view of the adjustment driver  830  and elastomer element  702  of the golf club head  800  of  FIG. 15A .  FIG. 17D  depicts a section view of the adjustment driver  830  and elastomer element  702  of  FIG. 17A .  FIG. 17E  depicts an additional perspective of the section view of the adjustment driver  830  and elastomer element  702  of  FIG. 17A . 
     As illustrated in  FIGS. 15D and 16 , the golf club head  800  includes a striking face  818  having a rear surface  819 . The golf club head  800  also includes a back portion  812  configured to support the elastomer element  702 . The golf club head  800  is made with a hollow body construction and the back portion  812  covers a substantial portion of the back of the golf club head  800 . The back portion  812  is located behind the striking face  818  and extends between the topline  807  and the sole  805  and from the heel  804  to the toe  806  forming a cavity  820 . The elastomer element  702  is disposed within the cavity  820 . As illustrated in  FIG. 15D . the striking face  818  can be formed separately and welded to the rest of the golf club head  800 . More specifically, the separately formed striking face portion can include a portion of the sole, forming an L-shaped striking face portion. In other embodiments, the striking face  818  may be formed integrally with the rest of the golf club. 
     The golf club head  800  includes an adjustment driver  830  much like the adjustment driver  330  described earlier and illustrated in  FIGS. 3A and 3B . The golf club head  800  also includes a deformable member  702  disposed between the striking face  818  and the adjustment driver  830 . The deformable member  702  can take the form of any of the elastomer elements described herein. The adjustment driver  830  is configured to retain the elastomer element  702  between the adjustment driver  830  and the striking face  818 , with the front portion  703  of the elastomer element  702  contacting the rear surface  819  of the striking face  818  and the rear portion  744  of the elastomer element  702  contacting the adjustment driver  830 . The adjustment driver can include an interface  834  configured to retain the elastomer element  702 . The interface  834  can include a recess with a lip  809  surrounding at least a portion of the elastomer element  702  as illustrated in  FIGS. 15D and 17A-17E . 
     The golf club head  800  can include an adjustment receiver  890 , much like the adjustment receiver  306  illustrated in  FIGS. 3A and 3B . As illustrated in  FIG. 16 , the adjustment receiver  890  can include an aperture formed in the back portion  812  of the golf club head  800 . The aperture can include a threaded portion  893 . Additionally, the adjustment receiver  890  can include a receiver shelf  895  for the adjustment driver  830  to engage when it is installed in the adjustment receiver  890  as illustrated in  FIG. 15D . The adjustment driver  830 , as illustrated in  FIGS. 15D and 17A-17E , can include a threaded portion  833  configured to engage the threaded portion  893  of the adjustment receiver  890 . Additionally, the adjustment driver  830  can include a flange  835  configured to engage the receiver shelf  895  of the adjustment receiver  890  when the adjustment driver  830  is installed in the adjustment receiver  890 . The receiver shelf  895  and flange  835  help to ensure the elastomer element properly and consistently engages the rear surface  819  of the striking face  818  and provides the support necessary for optimal performance. While the adjustment driver  330  discussed earlier is configured such that it may be adjusted after assembly, the preferred embodiment of the adjustment driver  830  illustrated in  FIGS. 15A-15D and 17A-17E  is configured to be installed to a set position during assembly and remain in that position. The receiver shelf  895  and flange  835  help to ensure the adjustment driver  830  is installed consistently and that the elastomer element properly and consistently engages the rear surface  819  of the striking face  818  and provides the support necessary for optimal performance. The adjustment driver  830  can also include a screw drive  832  configured to receive a tool and allow the adjustment driver  830  to be rotated relative to the golf club head  800 . Finally, the adjustment driver  830  can have a mass. In some embodiments, the mass of the golf club head can be adjusted by swapping out the adjustment driver  830  for another adjustment driver  830  having a different mass. The difference in mass can be achieved through the use of different materials for different adjustment drivers such as aluminum, brass, polymers, steel, titanium, tungsten, etc. In another embodiment, not illustrated, mass elements could be added to the adjustment driver to change the mass. In one embodiment, mass elements could be added to the recess of the adjustment driver. Additionally, the mass element added to the recess could also be used to change the distance between the rear portion of the elastomer element and the rear surface of the striking face, altering the compression of the elastomer element. 
       FIGS. 18-22  depict a golf club head  900  similar to the golf club head  800  depicted in  FIGS. 15A-15D . Golf club head  900  however includes a second deformable member  702 B in addition to a first deformable member  702 A.  FIG. 18  depicts a rear view of the golf club head  900 .  FIG. 19  depicts an exploded view of the golf club head  900  of  FIG. 18 .  FIG. 20  depicts a section view F-F of the golf club head  900 .  FIG. 21  depicts a section view G-G of the golf club head  900 .  FIG. 22  depicts a frontal view of the golf club head  900  of  FIG. 18 , including the supported regions. 
     As illustrated in  FIGS. 18-22 , the golf club head  900  includes a striking face  918  having a rear surface  919 . The golf club head  900  also includes a back portion  912  configured to support the first deformable member  702 A and the second deformable member  702 B. The first deformable member  702 A can be the same as the deformable member  700  described earlier. The first deformable member  702 A and a second deformable member  702 B can each take the form of any of the elastomer elements described herein. They may take the same form, or they make take different forms. The golf club head  900  is made with a hollow body construction and the back portion  912  covers a substantial portion of the back of the golf club head  900 . The back portion  912  is located behind the striking face  918  and extends between the topline  917  and the sole  905  from the heel  904  to the toe  906  forming a cavity  920 . In the preferred illustrated embodiments the first deformable member  702 A is spaced from and does not contact the second deformable member  702 B. In an alternative embodiment, the first deformable member  702 A may be spaced closely to and contact the second deformable member  702 B. 
     Much like golf club head  800 , the golf club head  900  includes an adjustment driver  830  configured to retain the first deformable member  702 A. The front portion  703 A of the first deformable member  702 A contacts the rear surface  919  of the striking face  918 . The back portion  912  of the golf club head  900  includes a back cover  913 . In the illustrated embodiment, the back cover  913  includes a recess  915  configured to retain the second deformable member  702 B such that the front portion  703 B of the second deformable member  702 B contacts the rear surface  919  of the striking face  918 . The back cover  913  also includes an aperture  914  for the adjustment driver  830 . In one embodiment, the second deformable member is attached to the back cover  913  with an adhesive. Additionally, the back cover  913  can be attached to the rest of the golf club head  900  with an adhesive, which may include, for example, double sided tape. In one embodiment, the striking face  918  of the golf club head  900  is made from a high density material such as steel, whereas the back cover  913  is made from a low density material, such as plastic, which may include for example, acrylonitrile butadiene styrene. In an alternative embodiment, the back cover may also be made of a high density material. 
     As illustrated in  FIG. 22 , the striking face includes a plurality of supported regions. The first supported region  742 A is defined by the portion of the rear surface  919  of the striking face  918  supported by the first deformable member  702 A, which is defined by the area inside the first supported region perimeter  740 A defined by the outer extent of the front portion  703 A of the first deformable member  702 A in contact with the rear surface  919  of the striking face  918 . The second supported region  742 B is defined by the portion of the rear surface  919  of the striking face  918  supported by the second deformable member  702 B, which is defined by the area inside the second supported region perimeter  740 B defined by the outer extent of the front portion  703 B of the second deformable member  702 B in contact with the rear surface  919  of the striking face  918 . The first supported region  742 A and second supported region  742 B wouldn&#39;t normally be visible from the front of the golf club head  900  but was added in  FIG. 22  for illustrative purposes. 
     The first geometric center  743 A of the first supported region  742 A is located a first supported region offset length SROL  1  toeward from the striking face heel reference plane  959 , measured parallel to the ground plane and parallel to the striking face  918  with the golf club head  900  in an address position. The second geometric center  743 B of the second supported region  742 B is located a second supported region offset length SROL  2  toeward from the striking face heel reference plane  959 , measured parallel to the ground plane and parallel to the striking face  918  with the golf club head  900  in an address position. 
     In a preferred embodiment, SROL  1  is approximately 36.0 mm and SROL  2  is approximately 17.6 mm. In a preferred embodiment SROL  1  is greater than SROL  2 . In a preferred embodiment, SROL  1  divided by SROL 2  is greater than 1.0. In a preferred embodiment, SROL  1  divided by SROL 2  is greater than 1.25. In a preferred embodiment, SROL  1  divided by SROL 2  is greater than 1.50. In a preferred embodiment, SROL  1  divided by SROL 2  is greater than 1.75. In a preferred embodiment, SROL  1  divided by SROL 2  is greater than 2.0. In an alternative embodiment, not illustrated, SROL  2  is greater than SROL  1 . 
     In one embodiment, the first deformable member  702 A is made of the same material as the second deformable member  702 B and thus has the same hardness. In an additional embodiment, the first deformable member  702 A is made of a material which has a greater hardness than the material of the second deformable member  702 B. In an alternative embodiment, the material of the first deformable member  702 A has a lower modulus than the material of the second deformable member  702 B. In one embodiment, the first deformable member  702 A has a Shore A 50 durometer and the second deformable member has a Shore A 10 durometer. In one embodiment, the first deformable member  702 A has a Shore A durometer greater than 25 and the second deformable member has a Shore A durometer less than 25. 
     It should be noted that the first deformable member could be housed, structured, or supported similarly to the second deformable member and also the second deformable member could be housed, structured, or supported similarly to the first deformable member. Additionally, the first deformable member and second deformable member could be housed, structured, or supported in any fashion described throughout this disclosure. 
       FIG. 23  depicts a perspective view of golf club head  900  and an additional embodiment of the second deformable member  702 C. The second deformable member  702 C is illustrated in an exploded fashion behind the golf club head  900 .  FIG. 24  depicts the second deformable member  702 C illustrated in  FIG. 23 .  FIG. 25  depicts a section view F-F of the golf club head  900  including the second deformable member  702 C illustrated in  FIGS. 23 and 24 . The back portion  912  of the golf club head  900  includes an aperture  930  configured to receive the second deformable member  702 C, or alternatively the second deformable member  702 B. The second deformable member  702 C, as illustrated in  FIGS. 23-25 , includes an annular groove  940  formed therein configured to engage the perimeter of the aperture  930  of the back portion  912  of the golf club head  900  and secure the second deformable member  702 C to the gold club head  900 . Portions of the second deformable member  702 C can be configured to deform as the second deformable member  702 C is installed in the aperture  930  of the golf club head  900  until the groove  940  engages the aperture  930 . 
     Although specific embodiments and aspects were described herein and specific examples were provided, the scope of the invention is not limited to those specific embodiments and examples. One skilled in the art will recognize other embodiments or improvements that are within the scope and spirit of the present invention. Therefore, the specific structure, acts, or media are disclosed only as illustrative embodiments. The scope of the invention is defined by the following claims and any equivalents therein.