Patent Publication Number: US-11020640-B2

Title: Multi-component putter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This claims the benefit of U.S. Provisional Patent Appl. No. 62/739,747, filed on Oct. 1, 2018, the contents all of which are incorporated fully herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to golf clubs and relates more particularly to a multi-component putter type golf club head. 
     BACKGROUND 
     In many putter-type golf club heads, there is a use of a weight distribution device, in order to vary the center of gravity or increase the moment of inertia (MOI) of the golf club head. Common weight distribution devices include removable weight ports in the heel and toe regions of the sole, weighted faceplate inserts, inserts for the back of portion of the face, and attachments for the outer perimeter of the toe and heel regions. In particular putter-type golf club heads, often use weight ports in the heel and toe regions that can be removable attached by a fastener, or permanently attached through a variety of epoxies, glues, or machining methods. The use of weight ports in the heel and toe regions, the increases the MOI in the putter head, thereby producing a straighter ball path after impact. 
     Although these weight ports in the heel and toe regions increase MOI, they increase the weight of the golf club head and can make the golf club head heavier than an ideal weight for a putter. In addition, installing weight ports into a golf club putter head requires a cavity or recess to place these weight ports into the putter head during manufacturing, thereby increasing the cost of that putter head. Additionally, the weight ports can cause vibrations within the cavity or recess during impact, when the golf club head contacts a golf ball. These cavities and recesses can cause the sound of the club head to change as well, creating a hollow sound within the club head. There is a need in the art to develop a putter having perimeter weighting and having an ideal weight for balanced putting without adding complicated structures such as weight ports. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates an exploded view of a blade putter type golf club head. 
         FIG. 1B  illustrates an isometric view of the blade putter type golf club head of  FIG. 1A . 
         FIG. 1C  illustrates a side view of the blade putter type golf club head of  FIG. 1A . 
         FIG. 2A  illustrates an exploded view of a blade putter type golf club head. 
         FIG. 2B  illustrates an isometric view of the blade putter type golf club head of  FIG. 2A . 
         FIG. 2C  illustrates a side view of the blade putter type golf club head of  FIG. 2A . 
         FIG. 3A  illustrates an exploded view of a crescent putter type golf club head. 
         FIG. 3B  illustrates an isometric view of the crescent putter type golf club head of  FIG. 3A . 
         FIG. 3C  illustrates a side view of the crescent putter type golf club head of  FIG. 3A . 
         FIG. 4A  illustrates an exploded view of a semi-circular putter type golf club head. 
         FIG. 4B  illustrates an isometric view of the semi-circular putter type golf club head of  FIG. 4A . 
         FIG. 4C  illustrates a side view of the semi-circular putter type golf club head of  FIG. 4A . 
         FIG. 5A  illustrates an exploded view of another semi-circular putter type golf club head. 
         FIG. 5B  illustrates an isometric view of the semi-circular putter type golf club head of  FIG. 5A . 
         FIG. 5C  illustrates a side view of the semi-circular putter type golf club head of  FIG. 5A . 
         FIG. 6A  illustrates an exploded view of a winged putter type golf club head. 
         FIG. 6B  illustrates an isometric view of the winged putter type golf club head of  FIG. 6A . 
         FIG. 6C  illustrates a side view of the winged putter type golf club head of  FIG. 6A . 
         FIG. 7A  illustrates an exploded view of a spade putter type golf club head. 
         FIG. 7B  illustrates an isometric view of the spade putter type golf club head of  FIG. 7A . 
         FIG. 7C  illustrates a side view of the spade putter type golf club head of  FIG. 7A . 
         FIG. 7D  illustrates a bottom perspective view of the spade putter type golf club head of  FIG. 7A . 
         FIG. 8A  illustrates an exploded view of a T-shaped putter type golf club head with periphery spans. 
         FIG. 8B  illustrates an isometric view of the T-shaped putter type golf club head with periphery spans of  FIG. 8A . 
         FIG. 8C  illustrates a side view of the T-shaped putter type golf club head with periphery spans of  FIG. 8A . 
         FIG. 8D  illustrates a bottom perspective view of the T-shaped putter type golf club head with periphery spans of  FIG. 8A . 
         FIG. 9A  illustrates an exploded view of a dual rail putter type golf club head. 
         FIG. 9B  illustrates an isometric view of the dual rail putter type golf club head of  FIG. 9A . 
         FIG. 9C  illustrates a side view of the dual rail putter type golf club head of  FIG. 9A . 
         FIG. 9D  illustrates a bottom perspective view of the dual rail putter type golf club head of  FIG. 9A . 
         FIG. 10A  illustrates an exploded view of a circular putter type golf club head. 
         FIG. 10B  illustrates an isometric view of the circular putter type golf club head of  FIG. 10A . 
         FIG. 10C  illustrates a side view of the circular putter type golf club head of  FIG. 10A . 
         FIG. 10D  illustrates a bottom perspective view of the circular putter type golf club head of  FIG. 10A . 
         FIG. 11A  illustrates an exploded view of a putter type golf club head with at least one strike face insert. 
         FIG. 11B  illustrates an exploded view of another putter type golf club head with at least one strike face insert. 
     
    
    
     Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings. 
     DESCRIPTION 
     I. Putter Golf Club Head 
     Described herein is a two part putter having an upper portion made of a first material such as low density metal (i.e., aluminum, but not limited to) and a lower portion made of a second material, such as a high density metal (i.e., steel, but not limited to). The upper portion has crown that spans from a strike face to a back edge. This upper portion is affixed to the lower portion and is farther from a ground plane than the lower portion. The lower portion, in most embodiments, has less than 35% of the total solid volume of the putter head, but greater than 45% of the mass. The lower portion provides a peripheral construction and a sole. This combination of peripheral construction and high density lower portion, results in an increase in MOI of at least 30%, over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single material such as a steel putter or a putter investment cast of a single material). 
     The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms “include,” and “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, device, or apparatus that comprises a list of elements is not necessarily limited to those elements but may include other elements not expressly listed or inherent to such process, method, system, article, device, or apparatus. 
     The terms “left,” “right,” “front,” “back,” “upper,” “lower,” “over,” “under,” “top,” “bottom,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the apparatus, methods, and/or articles of manufacture described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. 
     Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. 
     In many embodiments, the golf club head can comprise a putter-type golf club head (the putter type golf club head  100 ,  200 ,  300   400  . . . etc.).  FIGS. 1-12B  illustrate multiple embodiments of a putter-type golf club head having an upper portion and lower portion that are separately made of different materials and coupled together. The putter-type golf club head can be a mallet-type putter head, mid-mallet type putter head, a blade type putter head, a high MOI putter head, or any other type of putter-type golf club head. 
     In many embodiments, the putter-type golf club head can have a loft angle less than 10 degrees. In many embodiments, the loft angle of the club head can be between 0 and 5 degrees, between 0 and 6 degrees, between 0 and 7 degrees, or between 0 and 8 degrees. For example, the loft angle of the club head can be less than 10 degrees, less than 9 degrees, less than 8 degrees, less than 7 degrees, less than 6 degrees, or less than 5 degrees. For further example, the loft angle of the club head can be 0 degrees, 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, 7 degrees, 8 degrees, 9 degrees, or 10 degrees. 
     The putter-type golf club head comprises an upper portion and a lower portion. The golf club head can comprise a toe end and a heel end opposite the toe end. The putter-type golf club head can comprise a strike face. The putter-type golf club head can comprise a rear wall opposite the strike face. Further, the putter-type golf club head can comprise an alignment feature. Furthermore, the putter-type golf club head can comprise a hosel attached to the heel end of the golf club head. The hosel may be attached to the center of the putter-type golf club head. The hosel may be attached to the heel end of the putter-type golf club head. The hosel may be integrally formed with the upper portion of the putter-type golf club head. The hosel may be integrally formed with the lower portion of the putter-type golf club head. 
     The upper portion is made of a first material. The lower portion is made of a second material. The first material is different than the second material. The first material has a first density. The second material has a second density. The first density is not the same as the second density. 
     In many embodiments, the putter-type golf club head can have a mass that ranges between 340 and 385 grams. In other embodiments, the mass of the putter-type golf club head can range between 340 grams-345 grams, 345 grams-350 grams, 350 grams-355 grams, 355 grams-360 grams, 360 grams-365 grams, 365 grams-370 grams, 370 grams-375 grams, 375 grams-380 grams, or 380 grams-385 grams. In some embodiments, the mass of the putter-type golf club head can be 340 grams, 341 grams, 342 grams, 343 grams, 344 grams, 345 grams, 346 grams, 347 grams, 348 grams, 349 grams, 350 grams, 351 grams, 352 grams, 353 grams, 354 grams, 355 grams, 356 grams, 357 grams, 358 grams, 359 grams, 360 grams, 361 grams, 362 grams, 363 grams, 364 grams, 365 grams, 366 grams, 367 grams, 368 grams, 369 grams, 370 grams, 371 grams, 372 grams, 373 grams, 374 grams, 375 grams, 376 grams, 377 grams, 378 grams, 379 grams, 380 grams, 381 grams, 382 grams, 383 grams, 384 grams, or 385 grams. 
     In many embodiments, the putter type golf club head can comprise a club head volume ranging between 25 cc and 125 cc. In some embodiments, the club head volume can range between 25 cc-30 cc, 30 cc-35 cc, 35 cc-40 cc, 40 cc-45 cc, 45 cc-50 cc, 50 cc-55 cc, 55 cc-60 cc, 60 cc-65 cc, 65 cc-70 cc, 70 cc-75 cc, 75 cc-80 cc, 80 cc-85 cc, 85 cc-90 cc, 90 cc-95 cc, 95 cc-100 cc, 100 cc-105 cc, 105 cc-110 cc, 110 cc-115 cc, 115 cc-120 cc, or 120 cc-125 cc. In one embodiment, the club head volume can range between 40 cc-110 cc. In some embodiments, the club head volume can be greater than 25 cc, greater than 50 cc, greater than 75 cc, or greater than 100 cc. 
     In some embodiments, the putter type golf club head can comprise a strike face made of the first material. In other embodiments, the strike face can be made of the second material. In these embodiments, the material of the strike face can be any one or combination of the following: 8620 alloy steel (7.83 g/cc), S25C steel (7.85 g/cc), carbon steel (7.85 g/cc), maraging steel (8.00 g/cc), 17-4 stainless steel (7.81 g/cc), 303 stainless steel (8.03 g/cc), 304 stainless steel (8.00 g/cc), stainless steel alloy (7.75 g/cc-8.05 g/cc), tungsten (19.25 g/cc), aluminum (2.70 g/cc), aluminum alloy (2.64 g/cc-2.81 g/cc), ADC-12 (2.75 g/cc), or any metal suitable for creating a golf club head. In some embodiments, the strike face can be integrally formed to the upper portion. In other embodiments the strike face can be integrally formed to the lower portion. The strike face can be integrally formed to the club head by co-molding, injection molding, casting, additive manufacturing or other forming process. 
     Referring to  FIGS. 11A and 11B , in some embodiments, the putter type golf club head can comprise a strike face insert. In these embodiments, the strike face is independently formed prior to being coupled to the club head. The side of the strike face insert that will contact the club head can comprise geometry complementary to the geometry of the corresponding portion of the club head that will contact the strike face. In some embodiments, the strike face insert can be made of the first material or the second material. In other embodiments, the strike face insert can be made of a third material. In some embodiments, the strike face insert can be integrally formed with the upper portion or the lower portion. In other embodiments, the strike face insert can be separately formed from both the upper portion and the lower portion. 
     The strike face can be secured to the club head by being integrally formed to a portion of the club head or by a fastening means. In some embodiments, the strike face is secured to the upper portion. In these embodiments, the upper portion can comprise an insert cavity. The upper portion insert cavity functions to receive the strike face insert. Further, in these embodiments, when the insert is affixed to the upper portion, the upper portion encompasses and mates with the insert cavity. In other embodiments, the strike face is secured to the lower portion. In these embodiments, the lower portion can comprise an insert cavity. The lower portion insert cavity functions to receive the strike face insert. Further, in these embodiments, when the insert is affixed to the lower portion, the lower portion encompasses and mates with the insert cavity. The strike face can be secured by an adhesive such as glue, very high bond (VHB™) tape, epoxy or another adhesive. Alternately or additionally, the strike face can be secured by welding, soldering, screws, rivets, pins, mechanical interlock structure, or another fastening method. 
     The strike face insert of these embodiments can comprise any one or layered combination of the following: aluminum, stainless steel, copper, thermoplastic co-polyester elastomer (TPC), thermoplastic elastomer (TPE), thermoplastic urethane (TPU), steel, nickel, TPU/aluminum, TPE/aluminum, plastic/metal screen insert, polyethylene, polypropylene, polytetrafluoroethylene, polyisobutylene, polyvinyl chloride, PEBAX®, or any other desired material. PEBAX® is a polyether block amide that is a thermoplastic elastomer made of a flexible polyether and rigid polyamide. The rigid polyamide can comprise Nylon. The PEBAX® can comprise different compounds that correspond to different Shore D hardness values, polyether percentages, and/or polyamide percentages. In many embodiments, the PEBAX® can comprise a PEBAX® 4033 (Arkema, Paris France) or a PEBAX® 6333 (Arkema, Paris France). The PEBAX® 4033 (Arkema, Paris France) comprises a tetramethylene oxide (53% wt) and a Nylon 12. The PEBAX® 6333 (Arkema, Paris France) comprises a Nylon 11. In some embodiments, the face insert can comprise a material such as steel, steel alloys, tungsten, tungsten alloys, aluminum, aluminum alloys, titanium, titanium alloys, vanadium, vanadium alloys, chromium, chromium alloys, cobalt, cobalt alloys, nickel, nickel alloys, other metals, other metal alloys, composite polymer materials or any combination thereof. 
     The PEBAX® can comprise a percentage of polyether by volume. In some embodiments, the PEBAX® can comprise 0% to 10%, 10% to 20%, 15% to 30%, 20% to 30%, 30% to 40%, 30% to 50%, 30% to 60%, 40% to 50%, 40% to 60%, 50% to 60%, or 60% to 70% polyether by volume. For example, the PEBAX® can comprise 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% of polyether by volume. In some embodiments, the PEBAX® can comprise 0% to 10%, 10% to 20%, 15% to 30%, 20% to 30%, 30% to 40%, 40% to 50%, 40% to 60%, 50% to 60%, or 60% to 70% of polyamide by volume. For example, the PEBAX® can comprise 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% of polyamide by volume. As the percentage of polyether percentage increases, the hardness of the PEBAX® decreases. As the percentage of polyamide percentage increases, the hardness of the PEBAX® increases. For example, the PEBAX® 4033 (Arkema, Paris France) can comprise 40% to 60% polyether by volume and 15% to 30% polyamide by volume. For example, the PEBAX® 6333 (Arkema, Paris France) can comprise 15% to 30% polyether by volume and 40% to 60% polyamide by volume. 
     In many embodiments, the PEBAX® can comprise a hardness ranging from Shore 25D to Shore 75D. In some embodiments, the hardness of the PEBAX can range from Shore 25D to Shore 35D, Shore 35D to Shore 45D, Shore 36D to Shore 44D, Shore 38D to Shore 42D, Shore 45D to Shore 55D, Shore 55D to Shore 65D, Shore 56D to Shore 64D, Shore 60D to Shore 65D, or Shore 65D to Shore 75D. For example, the hardness of the PEBAX can be Shore D 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70. 
     In many embodiments, the PEBAX® 4033 (Arkema, Paris France) can comprise a lower hardness than the PEBAX® 6333 (Arkema, Paris France). In many embodiments, the PEBAX® 4033 (Arkema, Paris France) can comprise a hardness range of Shore 35D to Shore 55D. In some embodiments, the PEBAX® 4033 (Arkema, Paris France) can comprise a hardness range of Shore 38D to Shore 42D, or Shore 39D to Shore 41D. For example, the PEBAX® 4033 (Arkema, Paris France) can be comprise a Shore D hardness of 40. In many embodiments, the PEBAX® 6333 (Arkema, Paris France) can comprise a hardness range of Shore 50D to Shore 75D. In some embodiments, the PEBAX® 6333 (Arkema, Paris France) can comprise a hardness range of Shore 55D to Shore 70D, or Shore 60D to Shore 65D. For example, the PEBAX® 6333 (Arkema, Paris France) can comprise a Shore D hardness of 63. 
     In some embodiments, the face insert can comprise a two-component system. The two-component system can comprise a ball striking face plate and a face insert base. The ball striking face plate of the face insert can comprise a first insert material. The face insert base of the face insert can comprise a second insert material. In many embodiments, the first insert material of the ball striking face plate and the second material of the face insert base can be different. In some embodiments, the first insert material of the ball striking face plate and the second insert material of the face insert base can be similar. In many embodiments, the first insert material of the ball striking face plate can comprise a polymer type material. In some embodiments, the first insert material of the ball striking face plate can comprise a metallic material. In many embodiments, the second insert material of the face insert base can comprise a polymer type material. 
     The first insert material can comprise a metal such as steel, steel alloys, tungsten, tungsten alloys, aluminum, aluminum alloys, titanium, titanium alloys, vanadium, vanadium alloys, chromium, chromium alloys, cobalt, cobalt alloys, nickel, nickel alloys, other metals, other metal alloys, composite polymer materials or any combination thereof. 
     The first insert material or the second insert material can comprise a polymer type material. The polymer type material can comprise polyethylene, polypropylene, polytetrafluoroethylene, polyisobutylene, polyvinyl chloride, or any other polymer type material. In many embodiments, the face insert can comprise a PEBAX®. More specifically, the PEBAX® is a polyether block amide that is a thermoplastic elastomer made of a flexible polyether and rigid polyamide. The rigid polyamide can comprise Nylon. The PEBAX® can comprise different compounds that correspond to different Shore D hardness values, polyether percentages, and/or polyamide percentages. In many embodiments, the PEBAX® can comprise a PEBAX® 4033 (Arkema, Paris France) or a PEBAX® 6333 (Arkema, Paris France). The PEBAX® 4033 (Arkema, Paris France) comprises a tetramethylene oxide (53% wt) and a Nylon 12. The PEBAX® 6333 (Arkema, Paris France) comprises a Nylon 11. The first insert material and the second insert material can comprise similar polyether percentages, polyamide percentages, or Shore D hardness values as described above. 
     The ball striking face plate of the face insert can comprise a thickness. In many embodiments, the thickness of the ball striking face plate can range from 0.015 to 0.115 inch. In some embodiments, the thickness of the ball striking face plate can range from 0.015 to 0.045 inch, 0.020 to 0.050 inch, 0.025 to 0.055 inch, 0.050 to 0.100 inch, 0.055 to 0.105 inch, 0.060 to 0.110, or 0.065 to 0.115 inch. In some embodiments, the thickness of the ball striking face plate can be at least 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, 0.080, 0.085, 0.090, 0.095, 0.10, 0.105, 0.110, or 0.115 inch. In some embodiments, the thickness of the ball striking face plate can be greater than or equal to 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, 0.080, 0.085, 0.090, 0.095, 0.10, 0.105, 0.110, or 0.115 inch. In some embodiments, the thickness of the ball striking face plate can be less than or equal to 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, 0.080, 0.085, 0.090, 0.095, 0.10, 0.105, 0.110, or 0.115 inch. For example, the thickness of the ball striking face plate can be 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, 0.080, 0.085, 0.090, 0.095, 0.10, 0.105, 0.110, or 0.115 inch. 
     In other embodiments, the thickness of the ball striking face plate can range from 0.115 to 0.40 inch. In some embodiments, the thickness of the ball striking face plate can range from 0.115 to 0.20 inch, 0.15 to 0.30 inch, 0.20 to 0.30 inch, 0.25 to 0.35 inch, or 0.30 to 0.40 inch. In some embodiments, the thickness of the ball striking face plate can be at least 0.15, 0.20, 0.25, 0.30, 0.35, or 0.40 inch. In some embodiments, the thickness of the ball striking face plate can be greater than or equal to 0.15, 0.20, 0.25, 0.30, 0.35, or 0.40. In some embodiments, the thickness of the ball striking face plate can be less than or equal to 0.15, 0.20, 0.25, 0.30, 0.35, or 0.40 inch. For example, the thickness of the ball striking face plate can be 0.15, 0.20, 0.25, 0.30, 0.35, or 0.40 inch. 
     The face insert base of the face insert can comprise a thickness. In many embodiments, the thickness of the face insert base can range from 0.05 to 0.20 inch. In some embodiment, the thickness of the face insert base can range from 0.05 to 0.10 inch, or 0.10 to 0.20 inch. In some embodiments, the thickness of the face insert base can be at least 0.05, 0.10, 0.15, or 0.20 inch. In some embodiments, the thickness of the face insert base can be greater than or equal to 0.05, 0.10, 0.15, or 0.20 inch. In some embodiments, the thickness of the face insert base can be less than or equal to 0.05, 0.10, 0.15, or 0.20 inch. For example, the thickness of the face insert base can be 0.05, 0.10, 0.15, or 0.20 inch. 
     In other embodiments, the thickness of the face insert base can range from 0.20 to 0.80 inch. In some embodiments, the thickness of the face insert base can range from 0.20 to 0.50 inch, 0.30 to 0.60 inch, 0.40 to 0.70 inch, or 0.50 to 0.80 inch. In some embodiment, the thickness of the face insert base can range from 0.20 to 0.40 inch, 0.30 to 0.50 inch, 0.40 to 0.60 inch, 0.50 to 0.70 inch, or 0.60 to 0.80 inch. In some embodiments, the face insert base of the face insert can be at least 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, or 0.80 inch. In some embodiments, the face insert base of the face insert can be greater than or equal to 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, or 0.80 inch. In some embodiments, the face insert base of the face insert can be less than or equal to 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, or 0.80 inch. For example, the thickness of the face insert base can be 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, or 0.80 inch. 
     The face insert can be formed by a number of different processes. The different forming processes include the following: injection molding, casting, blow molding, compression molding, co-molding, laser forming, film insert molding, gas assist molding, rotational molding, thermoforming, laser cutting, 3-D printing, forging, stamping, electroforming, machining, molding, or any combination thereof. Further, the face insert can have any combination of hardness, volume, thickness, and forming processes described above. 
     In many embodiments, the upper portion of the putter-type golf club head having the first material comprises a first density ranging between 1.0 g/cc and 6.0 g/cc. The first density can range between 2.0 g/cc to 5.0 g/cc. In some embodiments, the first density can range between 1.0-1.25 g/cc, 1.25-1.5 g/cc, 1.5-1.75 g/cc, 1.75-2.0 g/cc, 2.0-2.25 g/cc, 2.25-2.5 g/cc, 2.5-2.75 g/cc, 2.75-3.0 g/cc, 3.25-3.5 g/cc, 3.5-3.75 g/cc, 3.75-4.0 g/cc, 4.0-4.25 g/cc, 4.25-4.5 g/cc, 4.5-4.75 g/cc, 4.75-5.0 g/cc, 5.0-5.25 g/cc, 5.0-5.25 g/cc, 5.25-5.5 g/cc, 5.5-5.75 g/cc, or 5.75-6.0 g/cc. In one embodiment, the first density of the lower portion can range between 2.0-3.0 g/cc. In some embodiments, the first density can be less 6.0 g/cc, less than 5.0 g/cc, less than 4.0 g/cc, less than 3.0 g/cc, or less than 2.0 g/cc. In some embodiments, the first density can be 1.25 g/cc, 1.50 g/cc, 1.75 g/cc, 2.0 g/cc, 2.25 g/cc, 2.50 g/cc, 2.75 g/cc, 3.0 g/cc, 3.25 g/cc, 3.50 g/cc, 3.75 g/cc, 4.0 g/cc, 4.25 g/cc, 4.50 g/cc, 4.75 glee, 5.0 g/cc, 5.25 g/cc, 5.50 g/cc, 5.75 g/cc, or 6.0 g/cc. 
     In many embodiments, the lower portion of the putter-type golf club head having the second material. The second material can comprise a density. The density is a second density to the first density of the first material in the upper portion. The second density of the second material of the lower portion can range between 7.0 g/cc and 20.0 g/cc. In some embodiments, the second density can range between 7.0-7.5 g/cc, 7.5-8.0 g/cc, 8.0-8.5 g/cc, 8.5-9.0 glee, 9.0-9.5 glee, 9.5-10.0 g/cc, 10.0-10.5 g/cc, 10.5-11.0 g/cc, 11.0-11.5 g/cc, 11.5-12.0 g/cc, 12.0-12.5 g/cc, 12.5-13.0 g/cc, 13.0-13.5 g/cc, 13.5-14.0 g/cc, 14.0-14.5 g/cc, 14.5-15.0 g/cc, 15.0-15.5 g/cc, 15.5-16.0 g/cc, 16.0-16.5 g/cc, 16.5-17.0 glee, 17.0-17.5 g/cc, 17.5-18.0 g/cc, 18.0-18.5 g/cc, 18.5-19.0 g/cc, or 19.0-19.5 g/cc, or 19.5-20.0 g/cc. In one embodiment, the second density of the second material in the lower portion can range between 8.0-9.0 g/cc. In some embodiments, the second density can be 7.0 g/cc, 7.5 g/cc, 8.0 g/cc, 8.5 g/cc, 9.0 g/cc, 9.5 g/cc, 10.0 g/cc, 10.5 g/cc, 11.0 g/cc, 11.5 g/cc, 12.0 g/cc, 12.5 g/cc, 13.0 g/cc, 13.5 g/cc, 14.0 g/cc, 14.5 g/cc, 15.0 g/cc, 15.5 g/cc, 16.0 g/cc, 16.5 g/cc, 17.0 g/cc, 17.5 g/cc, 18.0 g/cc, 18.5 g/cc, 19.0 g/cc, 19.5 g/cc, or 20.0 glee. In some embodiments, the second density of the lower portion can be at least 2 times greater than the first density, at least 3 times greater than the first density, at least 4 times greater than the first density, or at least 5 times greater than the first density. In some embodiments, the second density can be greater than 7.0 g/cc, greater than 9.0 g/cc, greater than 10.0 glee, greater than 11.0 g/cc, or greater than 12.0 g/cc. 
     The upper portion of the putter-type golf club having the first material can be made from any one or combination of the following: 8620 alloy steel (7.83 g/cc), S25C steel (7.85 g/cc), carbon steel (7.85 g/cc), maraging steel (8.00 g/cc), 17-4 stainless steel (7.81 g/cc), 303 stainless steel (8.03 g/cc), 304 stainless steel (8.00 g/cc), stainless steel alloy (7.75 g/cc-8.05 g/cc), tungsten (19.25 g/cc), aluminum (2.70 g/cc), aluminum alloy (2.64 g/cc-2.81 g/cc), ADC-12 (2.75 g/cc), or any metal suitable for creating a golf club head. In many embodiments, the upper portion is made of aluminum alloy or ADC-12. 
     The lower portion of the putter-type golf club having the second material can be made from any one or combination of the following: 8620 alloy steel (7.83 g/cc), S25C steel (7.85 g/cc), carbon steel (7.85 g/cc), maraging steel (8.00 g/cc), 17-4 stainless steel (7.81 g/cc), 303 stainless steel (8.03 g/cc), 304 stainless steel (8.00 g/cc), stainless steel alloy (7.75 g/cc-8.05 g/cc), tungsten (19.25 g/cc), aluminum (2.70 g/cc), aluminum alloy (2.64 g/cc-2.81 g/cc), ADC-12 (2.75 g/cc), or any metal suitable for creating a golf club head. In many embodiments, the lower portion is made of 304 stainless steel, 8620 alloy steel, 17-4 stainless steel, or 1380 stainless steel. However, the lower and upper portion are not made from the same one material or the same combination of materials. 
     Furthermore, the upper and lower portion of the putter-type golf club head can be joined in any one or combination of the following methods: welding, soldering, brazing, swedging, adhesion, epoxy, or mechanical fastening. In some embodiments, the upper and lower portion can be joined by adhesion with epoxy, polyurethanes, resins, hot melts, or any other adhesive. 
     A. Benefits 
     The putter-type golf club head provides MOI, CG, feel, and weighting benefits, in a putter-type golf club head with an upper and lower portion having different densities and/or without using mechanically fastened weights or weight ports. By creating an upper portion and lower portion of a putter-type golf club head from two different material, the weighting of the club head shifts towards the peripheries of the putter-type golf club head, without any weight ports or attachments to the heel end and toe end of the putter-type golf club head. This shift in weight, towards the peripheries of the putter-type golf club head, raises the MOI of the club head about the y-axis (Iyy), therefore preventing the rotation about the y-axis and assuring the strike face is square to a golf ball during impact. The increase in MOI about the y-axis helps achieve a straighter ball path and improve the outcome of off-centered hits (impact at the heel end or toe end). 
     By creating the putter-type golf club head from two portions of two different materials, the putter-type golf club head can be optimized to improve the MOI, while keeping the golf club head at a desirable overall weight. In some embodiments, the moment of inertia of the golf club head about the y-axis center of gravity is between 3500 g cm 2 -6500 g in t . In other embodiments the moment of inertia of the golf club head about the y-axis center of gravity can be between 3500 gcm 2 -4000 gcm 2 , 4000 g cm 2 -4500 gcm 2 , 4500 g cm 2 -5000 gcm 2 , 5000 gcm 2 -5500 gcm 2 , 5500 gcm 2 -6000 gcm 2 , or 6000 gcm 2 -6500 gcm 2 . 
     The putter-type golf club head with upper and lower portions of two different materials, increases the MOI about the y-axis center of gravity by at least 30% over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single material such as a steel putter or a putter investment cast of a single material). In some embodiments, the putter-type golf club head with upper and lower portions of two different materials, increases the MOI about the y-axis center of gravity by at least 35%, by at least 40%, by at least 45%, by at least 50%, by at least 55%, by at least 60%, by at least 65%, by at least 70%, by at least 75%, by at least 80%, by at least 85%, by at least 90%, by at least 95%, by at least 95%, by at least 100%, or by at least 105%, over a putter with the same volume, mass, and single material construction. 
     II. Embodiments 
     a. Blade Embodiment 
     In one embodiment, the putter-type golf club head can be a blade type putter head  100 . Referring to  FIGS. 1A and 1B , the blade type putter head  100  has an upper portion  104  and a lower portion  108 . The upper portion  104  is made from a first material having a first density and the lower portion  108  is made from a second material having a second density. The first density is less than the second density. The upper portion  104  and lower portion  108  combine to create a balanced putter head  100 , while maintaining a desirable volume and mass. 
     The lower portion  108  comprises a toe end  124 , a heel end  128  opposite the toe end  124 , a rear wall  132  opposite a front surface  112 , a rear portion  156 , and an under surface (not shown). The under surface and the upper portion  104  form a sole  168 . The rear wall  132  is opposite and approximately parallel to the front surface  112 . The toe end  124  is opposite the heel end  128 , while adjacent to the strike face  112  and the rear portion  156 . The rear portion  156  spans from the heel end  128  to the toe end  124 , while also extending away from the rear wall  132  and the front surface face  112 . The rear portion  156  is adjacent the sole. The under surface spans from the heel end  128  to the toe end  124  and is adjacent the rear portion  156  and the front surface  112 . 
     Further, the toe end  124 , heel end  128 , and front surface  112  of the lower portion  108  forms a recess  140 , wherein the recess extends inwards from the front surface  112 , towards the rear wall  132 . The recess functions to receive the upper portion  104 . In most embodiments, the recess  140  comprises a corresponding geometry similar or identical to that of the upper portion  104 . When the upper portion  104  is affixed to the lower portion  108 , the upper portion  104  encompasses and mates with the lower portion  108  to fit within the recess  140 . 
     The lower portion  108  of the blade type putter head  100  can further comprise an alignment feature  136 . The alignment feature  136  can be any one or combination of the following: a line, a circle, a dashed line, a triangle, a channel, or any other desired alignment feature  136 . Referring to  FIGS. 2A-2C , in some embodiments, the blade type putter head  200  can comprise an alignment feature  236  on the upper portion  204 , rather than the lower portion  208 . 
     The upper portion  104  of the blade type putter  100  head comprises a hitting surface  113  and an adhesion surface  115 . The hitting surface  113  comprises an upper edge  116  and a lower edge  121 , wherein the upper edge  116  is further from a ground plane  172  than the lower edge  116 . The ground plane  172  is tangent to the lower portion  108 , when the putter head is at an address position to strike a golf ball. The upper edge  116  is adjacent the hitting surface  113  and the adhesion surface  115 , while opposite the lower edge  121 . In most embodiments, the hitting surface  113  and adhesion surface  115  are parallel, however in other embodiments, the hitting surface  113  and adhesion surface  115  are not parallel. 
     When the upper portion  104  and lower portion  108  are joined, the adhesion surface  115  is affixed to the recess  140  of the lower portion  108 . The hitting surface  113  of the upper portion  104 , and the front surface  112  of the lower surface, align to form a strike face  120 , that will function to hit strike golf ball. 
     The lower edge  121  of the upper portion  104 , and under surface of the lower portion  108  combine to create the sole  168 . The sole  168  is perpendicular to the ground plane  172 , wherein the ground plane  172  is tangent to the sole  168 , when the putter  100  is at an address position to strike a golf ball. The sole  168  of the putter  100  extends from the toe end  124  of the putter head  100  to the heel end  128  of the putter head  100 . 
     Referring to  FIG. 1C , in most embodiments, the sole  168  of the putter head  100  can be perfectly flat. In some embodiments, the sole  168  of the putter head  100  can have a slight arch in a heel  128  to toe  124  direction, wherein the slight arch can be linear, or a function of a polynomial. In some embodiments, the sole  168  of the putter head  100  can have a strong arch in the heel  128  to toe  124  direction, wherein the strong arch can be linear, or a function of a polynomial. The sole  168  functions to provide a surface to rest the putter head  100  on the ground plane  172 . 
     The strike face  120  of the blade type putter head  100  comprises a strike face center point  176  and a loft plane  180 . The strike face center point  176  is equidistant from the lower edge  120  and upper edge  116  of the strike face  120 , as well as equidistant from the heel end  128  and toe end  124  of the blade type putter head  100 . The loft plane  180  is tangent to the strike face  112  of the blade type putter head  100 . Further, a midplane  184  intersects the strike face center point  176  and is perpendicular to the loft plane  180 . Furthermore, a y-axis  188  intersects the strike face center point  176  and is perpendicular to the ground plane  172 . 
     In some embodiments, when the lower portion  108  and the upper portion  104  are joined, the upper edge  116  of the upper portion  104  can protrude in a direction away from the strike face  120 , overlaying at least a portion of the rear wall  132  of the lower portion  108 . Further, the lower edge  121  of the upper portion  104  can protrude in a direction away from the strike face  120 , towards at least a portion of the under surface of the lower portion  108 , thereby making up a portion of the sole  168 . In these embodiments, the rear wall  132  of the lower portion  108  does not make up a portion of the sole  168 . 
     The combination of the low density first material upper portion  104  with the high density second material lower portion  108 , increases the MOI of the putter  100 , over a putter of unitary, solid block construction. The two part construction (upper portion  104  and lower portion  108 ) of the putter  100 , moves denser material towards the heel  128  and toe  124 , while placing lighter material (the upper portion  104 ) near the center, thereby increasing the MOI of the putter  100 , since more mass is further from the center of gravity. The denser material of the lower portion helps increase the MOI of the putter-type golf club head by shifting the weight of the putter head  100  towards the outer portions of the putter-type golf club head. A single material putter fails to allocate high density material to the periphery. In some embodiments, the putter-type golf club head  100  with upper  104  and lower portions  108  of two different materials, increases the MOI about the y-axis center of gravity by at least 15% over a putter with the same volume, mass, and single material construction. 
     b. Crescent Embodiment 
     In one embodiment, the putter-type golf club head can be a crescent-shaped putter head  300 . Referring to  FIG. 3A-3C , the crescent-shaped putter head  300  has a upper portion  304  and a lower portion  308 . The upper portion  304  is made from a first material have a first density and the lower portion  308  is made from a second material having a second density. The first density is less than the second density. The upper portion  304  and lower portion  308  combine to create a balanced putter head  300 , while maintaining a desirable volume and mass. The high density lower portion  308  and low density upper portion  308 , place more mass near the peripheries of the putter head  300 , thus increasing the MOI and stability over a putter with the same volume, mass, and single material construction. 
     As discussed above, the lower portion  308  is comprised of a high-density material (i.e., the second material). The lower portion  308  comprises a rear periphery  352 , a toe end  312 , a heel end  316 , a strike face  320 , a rear wall  332 , a back edge  334 , a crown  342 , and an under surface (not shown). The under surface and the upper portion  304  form a sole  368 . The toe end  312  is opposite the heel end  316 . The toe end  312  and the heel end  316  of the lower portion  308  respectively comprise a toe side periphery  356  and a heel side periphery  356 . The strike face  320  spans from the toe end  312  to the heel end  316  and is opposite the rear wall  332 . The rear wall  332  is opposite, and approximately parallel to, the strike face  320 . The lower portion further comprises a heel side periphery  360 , a toe side periphery  356 , a front edge  316 , and a upper edge  312 . 
     The front edge  348  is adjacent to the toe side periphery  356  and the heel side periphery  360 , and opposite to the rear periphery  352 . The toe side periphery  356  is adjacent to the front edge  348  and the rear periphery  352 , and opposite and to the heel side periphery  360 . The heel side periphery  360  is also adjacent to the front edge  348  and the rear periphery  352 , but opposite to the toe side periphery  356 . 
     In most embodiments, the toe side periphery  356  extends perpendicularly from the front edge  348 , towards the rear periphery  352 , such that a right angle (90° angle) is formed at the junction of the toe side periphery  356  and the front edge  348 . However, in other embodiments, the toe side periphery  356  can extend from the front edge  348  in any direction, such that any angle (0°-180°) can be formed at the junction of the toe side periphery  356  and the front edge  348 . Further, in most embodiments, the heel side periphery  360  extends perpendicularly from the front edge  348 , such that a right angle (90° angle) is formed at the junction of the heel side periphery  360  and the front edge  348 . However, in other embodiments, the heel side periphery  360  can extend from the front edge  348  in any direction, such that any angle (0°-180°) can be formed at the junction of the heel side periphery  360  and the front edge  348 . 
     The front edge  348 , toe side periphery  356 , and heel side periphery  360  form an aperture  364 . The aperture  364  is bounded by the front edge  348  the toe side periphery  356 , and the heel side periphery  360 . The aperture  364  shifts a majority of the volume and mass of the putter to the extremities of the lower portion  308 . The aperture  364  can comprise any shape, however in one embodiment the aperture  364  is approximately rectangular. In other embodiments, the aperture  364  can be circular, curvilinear, triangular, trapezoidal, parabolic, golf ball shaped, square, or any other desired geometric shape. 
     The upper portion  304  of the putter head  300  comprises a crown  342 , a front edge  370 , and a back edge  334 . The crown  342  extends away from the front edge  370  to the back edge  364  of the upper portion  304 . The under surface is opposite the crown  342 , spanning from the front edge  348  to the back edge  334 . 
     In some embodiments, the heel side periphery  360  and toe side periphery  356  can be parallel, while in some embodiments, the heel side periphery  360  and toe side periphery  356  are not parallel. In some embodiments, the rear periphery  352  and front edge  348  can be parallel, while in some embodiments, the rear periphery  352  and front edge  348  are not parallel. The rear periphery  352  of the crescent-shaped putter head  300  is approximately crescent-shaped, and therefore, the rear periphery  352  and front edge  348  are not parallel. The rear periphery  352  can be curvilinear spanning from the heel side periphery  360  to the toe side periphery  356 . The rear periphery  352  comprises a curve length measured along the rear periphery  352  from the junction between the heel side periphery  360  and the rear periphery  352  to the junction between the toe side periphery  356  and the rear periphery  352 . In some embodiments, the rear periphery  352  curve length can be between 4.5 inches and 6.5 inches. In some embodiments, the rear periphery curve length can be 4.5 inches-4.75 inches, 4.75 inches-5.0 inches, 5.0 inches-5.25 inches, 5.25 inches-5.5 inches, 5.5 inches-5.75 inches, 5.75 inches-6.0 inches, 6.0 inches-6.25 inches, or 6.25 inches-6.5 inches. 
     When the upper portion  304  and the lower portion  308  are joined, the crown  342  extends between the strike face  320  to the rear periphery  352 . The crown  342 , in most embodiments, spans approximately inward 25% of the total club head  300  width from the toe side periphery  356  and spans approximately inward 25% of the total club head  300  width from the heel side periphery  360 . In other embodiments, the crown  342  can, continuously or discontinuously, span the entire width of the total club head  300 , in a heel  316  to toe  312  direction. In some embodiments, the crown  342 , can span less than 90% of the total width of the club head  300 , less than 80% of the total width of the club head  300 , less than 70% of the total width of the club head  300 , less than 60% of the total width of the club head  300 , less than 50% of the total width of the club head  300 , less than 40% of the total width of the club head  300 , or less than 30% of the total width of the club head  300 . Further, in some embodiments, the crown  342  can be substantially flat from the strike face  320  to the back edge  334  or ascend from the strike face  320  to the back edge  334 . In most embodiments, the ascent or descent of the crown  342  can be linear, curvilinear, parabolic, sinusoidal, or a function of polynomial. 
     The crown  342  further comprises an alignment trough  355 , wherein the alignment trough  355  is equidistant from the heel end  316  and the toe end  312 . The alignment trough  355  is adjacent the rear wall  328  and approximately perpendicular to the strike face. The alignment trough  356  is bounded by the back edge  334 , the rear wall  332 , and the crown  342  on the heel end  316  and the toe end  312 . In most embodiments, the alignment trough is approximately the width of a golf ball (approximately 4.27 cm) to provide the viewer a visual alignment field that extends the width of the golf ball. 
     Furthermore, the upper portion  304  of the putter head  300  can comprise one or more alignment features  344  on the crown  342 . The alignment feature  344  can be any one or combination of the following: a line, a series of lines, milling troughs, a circle, a dashed line, a triangle, a channel, or any other desired alignment feature  344 . The alignment features  344  can be equally spaced on the entire crown  342 , a portion of the crown  342 , or the alignment trough  355 . The alignment features  344 , extending along the alignment trough  355 , function to provide the viewer a visual alignment field that extends the width of the golf ball, from the rear wall  332  to the back edge  334  of the putter  300 . The goal is to align the entire putter  300  with the golf ball using these alignment features  344  along the crown  342  and/or the alignment trough  355 . 
     Referring to  FIG. 3C , the upper portion  304  can be affixed to the lower portion  308  such that the upper portion  304  is further from a ground plane than the lower portion  308 , wherein the ground plane  372  is tangent to the lower portion  304 , when the putter head  300  is at an address position to strike a golf ball. 
     Referring to  FIG. 3C , the strike face  320  of the putter head  300  comprises a strike face center point  376  and a loft plane  380 . The strike face center point  376  is equidistant from the crown  342  and the under surface of the upper portion  304 , as well as equidistant from the heel end  316  and toe end  312  of the putter head  300 . The loft plane  380  is tangent to the strike face  320  of the putter head  300 . Further, a midplane  316  intersects the strike face center point  376  and is perpendicular to the loft plane  380 . Furthermore, referring to  FIG. 3B , a y-axis  388  intersects the midplane  384 , and is perpendicular to the ground plane  372 . 
     When the upper portion  304  and lower portion  308  are joined such that the heel end  316  overlays at least a portion of the toe side periphery  356 . Further, when the upper portion  304  and lower portion  308  are joined such that the toe end  312  overlays at least a portion of the heel side periphery  360 . Further still, when the upper portion  304  and lower portion  308  are joined such that the strike face  320  overlays at least a portion of the front edge  316 . Finally, the upper portion  304  and lower portion  308  are joined such that the back edge  364  overlays at least a portion of the rear periphery  332 . 
     The front edge  316 , rear periphery  332 , toe side periphery  356 , and heel side periphery  360  of the lower portion  308 , combined with the upper portion  304 , create the sole  368 . The sole  368  is perpendicular to the ground plane  372 , wherein the ground plane  372  is tangent to the sole  368 , when the putter head  300  is at an address position to strike a golf ball. The sole  368  of the putter head  300  extends from the toe end  312  of the putter head  300  to the heel end  316  of the putter head  300 . 
     In most embodiments, the sole  368  of the putter head  300  can be perfectly flat. In some embodiments, the sole  368  of the putter head  300  can have a slight arch in a heel  324  to toe  320  direction, wherein the slight arch can be linear, or a function of a polynomial. In some embodiments, the sole  368  of the putter head  300  can have a strong arch in the heel  324  to toe  320  direction, wherein the strong arch can be linear, or a function of a polynomial. The sole  368  functions to provide a surface to rest the putter head  300  on the ground plane  372 . 
     Referring to  FIG. 3A , in one embodiment, the lower portion  308  can further comprise a toe mass  341  and a heel mass  343 . The toe mass  341  and heel mass  343  are integral to the lower portion  308  and are in contact with the toe side periphery  356  and heel side periphery  360 , respectively. The toe mass  341  and heel mass  343  extend from the lower portion  308 , in a direction away from the ground plane  372 , and toward the upper portion  304 . The toe mass  341  and heel mass  343  provide a means to position and align the upper portion  304  with the lower portion  308  of the putter head  300 . 
     Furthermore, the toe mass  341  and heel mass  343  provide an additional means of adding weight to the perimeters for increasing the MOI of the crescent-shaped putter head  300  when compared with putters without these mass features. These mass features can have weights that range from 2-5 grams, 3-7 grams or 1-6 grams. The mass features can have all the same weight or be different weight within the ranges provided above. The weight of the mass features can be 1 gram, 2 grams, 3 grams, 4 grams, 5 grams, 6 grams, or 7 grams. The toe mass  341  and a heel mass  343  can respectively be any one or combination of the following shapes: rectangular, triangular, pyramidal, spherical, crescent-shaped, square, cylindrical, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     Referring to  FIG. 3A , the toe mass  341  and heel mass  343  can be positioned away from the rear periphery  352 , wherein the toe mass  341  and heel mass  343  do not touch or intersect with the rear periphery  352 . However, in other embodiments, the toe mass  341  and heel mass  343 , can be positioned on the rear periphery  352 , wherein the toe mass  341  and heel mass  343  are integral to and intersect the rear periphery  352 . 
     In one embodiment, the toe mass  341  is positioned on the front edge  348 , at the junction of the toe side periphery  356  and the front edge  348 , however in other embodiments the toe mass  341  can be positioned anywhere along the toe side periphery  356 . In one embodiment, the heel mass  343 , is positioned on the front edge  348 , at the junction of the heel side periphery  360  and the front edge  348 , however in other embodiments the heel mass  343  can be positioned anywhere along the heel side periphery  360 . 
     The toe mass  341  and heel mass  343  provide areas of concentrated mass, such that the toe mass  341  and heel mass  343  function to increase the moment of inertia of the putter head  300 . The placement of the toe mass  341  and the heel mass  343  on or near the front edge  316  and on or near the toe side periphery  356  and heel side periphery  360 , respectively, increases the MOI since the toe mass  341  and the heel mass  343  are farther from a center of gravity of the putter  300 . The toe mass  341  and the heel mass  343  can be integrally formed from the second material, wherein the second material is denser than the first material. 
     The toe mass  341  and heel mass  343  offer dual functionalities, such that the toe mass  341  and heel mass  343  function not only to increase the MOI of the putter  300  but provide additional surfaces for the upper portion  304  to join to the lower portion  308 . Therefore, the toe mass  341  can also be referred to as a front toe adhesion portion  341  and the heel mass  343  can also be referred to as a front heel adhesion portion  343 . 
     In some embodiments, the under surface, crown  342 , front edge  370 , and back edge  334  of the upper portion  304 , can form a first cavity (not shown). The first cavity extends inwards from the under surface, on the toe end  312 , towards the crown  342  but does not reach the crown  342 . The first cavity is bounded by the back edge  334 , the crown  342 , and the front edge  370 . The first cavity functions to receive the toe mass  341  of the lower portion  308 . 
     In some embodiments, the under surface, crown  342 , front edge  370 , and back edge  334  of the upper portion  304 , can form a second cavity (not shown). The second cavity extends inwards from the under surface, on the heel end  316 , towards the crown  342  but does not reach the crown  342 . The second cavity is bounded by the back edge  334 , the crown  342 , and the front edge  370 . The second cavity functions to receive the heel mass  343  of the lower portion  308 . 
     The first and second cavities can comprise any desired geometry. However, in most embodiments, the first and second cavity comprise a geometry similar or identical to that of the corresponding toe mass  341  or the heel mass  343 . Further, when the upper portion  304  is affixed to the lower portion  308 , the first cavity is positioned such that the first cavity encompasses the toe mass  341 , and the second cavity is positioned such that the second cavity encompasses the heel mass  343 . 
     The combination of the low density first material upper portion  304  with the high density second material lower portion  308 , creates a high MOI putter  300 , without creating an extremely heavy putter. The large aperture  364  formed by the rear wall  332 , the rear periphery  352 , the toe side periphery  356 , and the heel side periphery  360  of the lower portion  308  forms a dense, yet low volume portion that increases the MOI of the putter, in comparison to a putter milled from a single material. A single material putter fails to allocate high density material to the periphery, while maintaining a desirable volume (50 cc-75 cc) and mass (340 grams-385 grams). 
     The lower portion  308 , in most embodiments, comprises less than 38% of a volume of the putter  300 . In some embodiments, the lower portion  308  comprises less than 37% of the total volume of the putter  300 , less than 36% of the total volume of the putter  300 , less than 35% of the total volume of the putter  300 , less than 34% of the total volume of the putter  300 , less than 33% of the total volume of the putter  300 , less than 32% of the total volume of the putter  300 , less than 31% of the total volume of the putter  300 , less than 30% of the total volume of the putter  300 , less than 29% of the total volume of the putter  300 , less than 28% of the total volume of the putter  300 , or less than 27% of the total volume of the putter  300 . 
     Although the lower portion  308  comprises less than half of the volume of the putter  300 , the lower portion  308  comprises at least 45% of an overall mass of the putter  300 . In some embodiments, the lower portion  308  comprises at least 46% of the mass of the putter  300 , at least 46% of the mass of the putter  300 , at least 47% of the mass of the putter  300 , at least 48% of the mass of the putter  300 , at least 49% of the mass of the putter  300 , at least 50% of the mass of the putter  300 , at least 51% of the mass of the putter  300 , at least 52% of the mass of the putter  300 , at least 53% of the mass of the putter  300 , at least 54% of the mass of the putter  300 , or at least 55% of the overall mass of the putter  300 . 
     The beneficial shift of mass to the periphery of the putter head  300  increases the MOI of the putter  300 , over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single stainless steel block, or a putter investment cast of a single material). 
     c. Semi-Circular Embodiment 
     In one embodiment, the putter-type golf club head can be a semi-circular shaped putter head  400 . Referring to  FIG. 4A-4C , the semi-circular putter head  400  has an upper portion  404  and a lower portion  408 . The upper portion  404  is made from a first material have a first density and the lower portion  408  is made from a second material having a second density. The first density is less than the second density. The upper portion  404  and lower portion  408  combine to create a high-MOI putter head  400  (5000 g·cm 2 -6500 g·cm 2 ), while maintaining a desirable volume and mass. 
     As discussed above, the lower portion  408  is comprised of a high-density material (i.e., the second material). The lower portion  408  comprises a front edge  448 , a rear periphery  452 , a toe side span  456 , and a heel side span  460 . The lower portion  408  and an under surface of the top portion  404  combine to create a sole  468 . The front edge  448  is adjacent to the toe side span  456  and the heel side span  460 , and opposite to the rear periphery  452 . The toe side span  456  is adjacent to the front edge  448  and the rear periphery  452 , and opposite and to the heel side span  460 . The heel side span  460  is also adjacent to the front edge  448  and the rear periphery  452 , but opposite to the toe side span  456 . The toe side span  456  and heel side span  460 , extend beyond the rear periphery  448  of the upper portion  404 . In some embodiments, the heel side span  460  and toe side span  456  can be parallel, while in some embodiments, the heel side span  460  and toe side span  456  are not parallel. In some embodiments, the rear periphery  452  and front edge  448  can be parallel, while in some embodiments, the rear periphery  452  and front edge  448  are not parallel. In this embodiment, the rear periphery  452  is approximately semi-circular, thus the rear periphery  452  and front edge  448  are not parallel. 
     In most embodiments, the toe side span  456  extends perpendicularly from the front edge  448 , such that a right angle (90° angle) is formed at the junction of the toe side span  456  and the front edge  448 . However, in other embodiments, the toe side span  456  can extend from the front edge  448  in any direction, such that any angle)(0°-180° can be formed at the junction of the toe side span  456  and the front edge  448 . Further, in most embodiments, the heel side span  460  extends perpendicularly from the front edge  448 , such that a right angle (90° angle) is formed at the junction of the heel side span  460  and the front edge  448 . However, in other embodiments, the heel side span  460  can extend from the front edge  448  in any direction, such that any angle) (0°-180° can be formed at the junction of the heel side span  460  and the front edge  448 . 
     The front edge  448 , toe side span  456 , and heel side span  460  form a gap  464 . The gap  464  is bounded by the front edge  448 , the toe side span  456 , and the heel side span  460 . The gap  464  formed by the front edge  448 , the toe side span  456 , and the heel side span  460  shifts a majority of the volume and mass of the putter to the extremities of the lower portion  408 . The gap  464  can comprise any shape, however in one embodiment the gap is approximately rectangular. In other embodiments, the gap  464  can be circular, curvilinear, triangular, trapezoidal, parabolic, golf ball shaped, square, or any other desired geometric shape. 
     The upper portion  404  of the putter head  400  comprises a toe end  412 , a heel end  416 , a strike face  420 , a rear wall  432 , a back edge  434 , a crown  442 , and an under surface (not pictured). The toe end  412  is opposite the heel end  416 . The strike face  420  spans from the toe end  412  to the heel end  416  and is opposite the rear wall  432 . The rear wall  432  is opposite, and approximately parallel to the strike face  420 . The crown  442  extends away from the strike face  420  to the back edge  434  of the upper portion  404 . Furthermore, the under surface is opposite the crown  442 , spanning from the strike face  420  to the back edge  434 . 
     The crown  442  further descends from the strike face  420  to the back edge  434 . Additionally, the crown  442  extends away from the strike face  420 , over the front edge  448  of lower portion  408 , and to the back edge  434  of the upper portion  404 . The crown  442 , in most embodiments, spans approximately inward 25% of the total club head  400  width from the toe side span  456  and spans approximately inward 25% of the total club head  400  width from the heel side span  460 . In other embodiments, the crown  442  can, continuously or discontinuously, span the entire width of the total club head  400 , in a heel to toe direction. In some embodiments, the crown  442 , can span less than 90% of the total width of the club head  400 , less than 90% of the total width of the club head  400 , less than 80% of the total width of the club head  400 , less than 70% of the total width of the club head  400 , less than 60% of the total width of the club head  400 , less than 50% of the total width of the club head  400 , less than 40% of the total width of the club head  400 , or less than 30% of the total width of the club head  400 . Further, in some embodiments, the crown  442  can be substantially flat from the strike face  420  to the back edge  434  or ascend from the strike face  420  to the back edge  434 . In most embodiments, the ascent or descent of the crown  442  can be linear, curvilinear, parabolic, sinusoidal, or a function of polynomial. 
     The crown  442  further comprises an alignment trough  455 , wherein the alignment trough  455  is equidistant from the heel end  416  and the toe end  412 . The alignment trough  455  is adjacent the rear wall  432  and approximately perpendicular to the strike face  420 . The alignment trough  455  is bounded by the back edge  434 , the rear wall  432 , and the crown  442  on the heel end  416  and the toe end  412 . In most embodiments, the alignment trough  455  is approximately the width of a golf ball (approximately 4.27 cm) to provide the viewer a visual alignment field that extends the width of the golf ball. 
     Furthermore, the upper portion  404  of the putter head  400  can comprise one or more alignment features  444  on the crown  442 . The alignment feature  444  can be any one or combination of the following: a line, a series of lines, milling troughs, a circle, a dashed line, a triangle, a channel, or any other desired alignment feature  444 . The alignment features  444  can be equally spaced on the entire crown  442 , a portion of the crown  442 , or the alignment trough  455 . The alignment features  444 , extending along the alignment trough  455 , function to provide the viewer a visual alignment field that extends the width of the golf ball, from the rear wall  432  to the back edge  434  of the putter  400 . The goal is to align the entire putter  400  with the golf ball using these alignment features  444  along the crown  442  and/or the alignment trough  455 . 
     Referring to  FIG. 4C , the upper portion  404  is affixed to the lower portion  408  such that the upper portion  404  is further from a ground plane  472  than the lower portion  408 , wherein the ground plane  472  is tangent to the lower portion  404 , when the putter head  400  is at an address position to strike a golf ball. 
     Further, the strike face  420  of the putter head  400  comprises a strike face center point  476  and a loft plane  480 . The strike face center point  476  is equidistant from the crown  442  and the undersurface of the upper portion  404 , as well as equidistant from the heel end  416  and toe end  412  of the putter head  400 . The loft plane  480  is tangent to the strike face  420  of the putter head  400 . Further, a midplane  484  intersects the strike face center point  476  and is perpendicular to the loft plane  480 . Furthermore, a y-axis  488  intersects the midplane  484 , and is perpendicular to the ground plane  472 . 
     When the upper portion  404  and lower portion  408  are joined such that the heel end  416  overlays at least a portion of the toe side span  456 . Further, when the upper portion  404  and lower portion  408  are joined such that the toe end  412  overlays at least a portion of the heel side span  460 . Further still, when the upper portion  404  and lower portion  408  are joined such that the strike face  420  overlays at least a portion of the front edge  448 . Finally, the upper portion  404  and lower portion  408  are joined such that the back edge  434  overlays at least a portion of the rear periphery  452 . 
     The rear periphery  452  can be curvilinear spanning from the heel side  416  to the toe side  416 . The rear periphery  452  comprises a curve length measured along the rear periphery  452  from the junction between the heel side  416  and the rear periphery  452  to the junction between the toe side  416  and the rear periphery  452 . In some embodiments, the rear periphery  452  curve length can be between 4.5 inches and 8.0 inches. In some embodiments, the rear periphery  452  curve length can be 4.5 inches-4.75 inches, 4.75 inches-5.0 inches, 5.0 inches-5.25 inches, 5.25 inches-5.5 inches, 5.5 inches-5.75 inches, 5.75 inches-6.0 inches, 6.0 inches-6.25 inches, 6.25 inches-6.5 inches, 6.5 inches-6.75 inches, 6.75 inches-7.0 inches, 7.25 inches-7.50 inches, 7.50 inches-7.75 inches, or 7.75 inches-8.0 inches. 
     The front edge  448 , rear periphery  452 , toe side span  456 , and heel side span  460  of the lower portion  408 , combined with the upper portion  404 , create the sole  468 . The sole  468  is perpendicular to the ground plane  472 , wherein the ground plane  472  is tangent to the sole  468 , when the putter head  400  is at an address position to strike a golf ball. The sole  468  of the putter head  400  extends from the toe end  412  of the putter head  400  to the heel end  416  of the putter head  400 . 
     In most embodiments, the sole  468  of the putter head  400  can be perfectly flat. In some embodiments, the sole  468  of the putter head  400  can have a slight arch in a heel  416  to toe  412  direction, wherein the slight arch can be linear, or a function of a polynomial. In some embodiments, the sole  468  of the putter head  400  can have a strong arch in the heel  416  to toe  412  direction, wherein the strong arch can be linear, or a function of a polynomial. The sole  468  functions to provide a surface to rest the putter head  400  on the ground plane  472 . 
     Referring to  FIG. 4A , in one embodiment, the lower portion  408  can further comprise a front toe mass  441  and a front heel mass  443 . The front toe mass  441 , front heel mass  443  are integral to the lower portion  408 . The front toe mass  441  and front heel mass  443  extend from the lower portion  408 , in a direction away from the ground plane  472 , and toward the upper portion  404 . These mass portions provide a means to position and align the upper portion  404  with the lower portion  408  of the putter head  400 . Furthermore, these mass portions (i.e., the front toe mass  441  and front heel mass  443 ) provide an additional means of adding weight to the perimeters for increasing the MOI of the putter  400  over putters without these mass features. These mass features can have weight that range from 2-5 grams, 3-7 grams or 1-6 grams. The mass features can have all the same weight or be different weight within the ranges provided above. The mass features can be 1 gram, 2 grams, 3 grams, 4 grams, 5 grams, 6 grams, or 7 grams. The front toe mass  441  and a front heel mass  443  can respectively be any one or combination of the following shapes: rectangular, triangular, pyramidal, spherical, semi-circular, square, cylindrical, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     In  FIG. 4A , the front toe mass  441  and front heel mass  443  are positioned away from the rear periphery  452 , wherein the front toe mass  441  and front heel mass  443  do not touch or intersect with the rear periphery  452 . However, referring to  FIG. 5A-5C , an alternate semi-circular shaped putter  500  is illustrated below. Putter  500  comprises the same features as putter  400 , however the front toe mass  541  and front heel mass  543  of putter  500 , are positioned on the rear periphery  552 , wherein the front toe mass  541  and front heel mass  53  are integral to and intersect the rear periphery  452 . 
     In one embodiment, the front toe mass  441  is positioned on the front edge  448 , at the junction of the toe side span  456  and the front edge  448 , however in other embodiments the front toe mass  441  can be positioned anywhere along the toe side span  456 . In one embodiment, the front heel mass  443 , is positioned on the front edge  448 , at the junction of the heel side span  460  and the front edge  448 , however in other embodiments the front heel mass  443  can be positioned anywhere along the heel side span  460 . 
     The front toe mass  441  and front heel mass  443  provide areas of concentrated mass, such that each mass  441 ,  443  function to increase the moment of inertia of the putter head  400 . The placement of each mass  441 ,  443  on the front edge  448  and spans  456 ,  460  increases the MOI since each mass  441 ,  443  since each mass is farther from a center of gravity of the putter  400 . Each mass  441 ,  443  on the periphery  448  and spans  456 ,  460  is integrally formed from the second material, wherein the second material is denser than the first material. 
     The front toe mass  441  and front heel mass  443  offer dual functionalities, such that the front toe mass  441  and front heel mass  443  function not only to increase the MOI of the putter  400  but provide additional surfaces for the upper portion  404  to join to the lower portion  408 . Therefore, the front toe mass  441  can also be referred to as a front toe adhesion portion  441  and the front heel mass  443  can also be referred to as a front heel adhesion portion  443 . 
     In some embodiments, the under surface, strike face  420 , and rear wall  432  of the upper portion  408 , can form a first cavity (not shown). The first cavity extends inwards from the under surface, on the toe end  412 , towards the crown  442  but does not reach the crown  442 . The first cavity is bounded by the rear wall  432 , the strike face  420 , and the toe  412 . The first cavity functions to receive the front toe mass  441  of the lower portion  408 . 
     In some embodiments, the under surface, strike face  420 , and rear wall  432  of the upper portion  408 , can form a second cavity (not shown). The second cavity extends inwards from the under surface, on the heel end  416 , towards the crown  442  but does not reach the crown  442 . The second cavity is bounded by the rear wall  432 , the strike face  420 , and the heel  416 . The second cavity functions to receive the front heel mass  443  of the lower portion  408 . 
     The first and second cavity can comprise any desired geometry, however in most embodiments, the first and second cavity comprise a geometry similar or identical to that of the front toe mass  441  and the front heel mass  443 . Further, when the upper portion  704  is affixed to the lower portion  408 , the first cavity is positioned such that the first cavity encompasses the front toe mass  441 , and the second cavity is positioned such that the second cavity encompasses the front heel mass  443 . 
     The combination of the low density first material upper portion  404  with the high density second material lower portion  408 , creates a high MOI putter  400 , without creating an extremely heavy putter. The large gap  464  formed by the rear periphery  452  and the spans  456 ,  460  of the lower portion  408  forms a dense, yet low volume portion that increases the MOI of the putter, in comparison to a putter milled from a single material. A single material putter fails to allocate high density material to the periphery, while maintaining a desirable volume (75 cc-100 cc) and mass (340 grams-385 grams). 
     The lower portion  408 , in most embodiments, comprises less than 38% of a volume of the putter  400 . In some embodiments, the lower portion  408  comprises less than 37% of the total volume of the putter  400 , less than 36% of the total volume of the putter  400 , less than 35% of the total volume of the putter  400 , less than 34% of the total volume of the putter  400 , less than 33% of the total volume of the putter  400 , less than 32% of the total volume of the putter  400 , less than 31% of the total volume of the putter  400 , less than 30% of the total volume of the putter  400 , less than 29% of the total volume of the putter  400 , less than 28% of the total volume of the putter  400 , or less than 27% of the total volume of the putter  400 . 
     Although the lower portion  408  comprises less than half of the volume of the putter  400 , the lower portion  408  comprises at least 45% of an overall mass of the putter  400 . In some embodiments, the lower portion  408  comprises at least 46% of the mass of the putter  400 , at least 46% of the mass of the putter  400 , at least 47% of the mass of the putter  400 , at least 48% of the mass of the putter  400 , at least 49% of the mass of the putter  400 , at least 50% of the mass of the putter  400 , at least 51% of the mass of the putter  400 , at least 52% of the mass of the putter  400 , at least 53% of the mass of the putter  400 , at least 54% of the mass of the putter  400 , or at least 55% of the mass of the putter  400 . 
     The beneficial shift of mass to the periphery of the putter head  400 , through the use of a high density, low volume lower portion  408 , increases the MOI of the putter  400 , over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single stainless steel block, or a putter investment cast of a single material). 
     d. Winged Embodiment 
     In one embodiment, the putter-type golf club head can be a winged shaped putter head with periphery spans  600 . Referring to  FIGS. 6A and 6B , the winged shaped putter head  600  has a upper portion  604  and a lower portion  608 . The upper portion  604  is made from a first material have a first density and the lower portion  608  is made from a second material having a second density. The first density is less than the second density. The upper portion  604  and lower portion  608  combine to create a high-MOI putter head  600  (5000 gcm 2 -6500 gcm 2 ), while maintaining a desirable volume and mass. 
     As discussed above, the lower portion  608  is comprised of a high-density material (i.e., the second material). The lower portion  608  comprises a front periphery  648 , a sole  668 , a rear periphery  652 , a toe side wing  656 , and a heel side wing  660 . As discussed below,  FIG. 6C , the front periphery  648 , rear periphery  652 , toe side wing  656 , and heel side wing  660  of the lower portion  608 , combined with the upper portion  604 , create a sole  668 . The front periphery  648  is adjacent to the toe side periphery  656  and the heel side periphery  660 , and opposite to the rear periphery  652 . The toe side wing  656  is adjacent to the front periphery  648  and the rear periphery  652 , and opposite to the heel side wing  660 . The heel side wing  660  is also adjacent to the front periphery  648  and the rear periphery  652 , but opposite to the toe side wing  656 . The toe side wing  656  and heel side wing  660 , extend beyond the rear periphery  648  of the upper portion  604 . In some embodiments, the heel side wing  660  and toe side wing  656  can be parallel, while in some embodiments, the heel side wing  660  and toe side wing  656  are not parallel. In some embodiments, the rear periphery  652  and front periphery  648  can be parallel, while in some embodiments, the rear periphery  652  and front periphery  648  are not parallel. 
     In most embodiments, the toe side wing  656  extends perpendicularly from the rear periphery  652 , such that a right angle (90° angle) is formed at the junction of the toe side wing  656  and the rear periphery  652 . However, in other embodiments, the toe side wing  656  can extend from the rear periphery  652  in any direction, such that any angle)(0°-180° can be formed at the junction of the toe side wing  656  and the rear periphery  652 . Further, in most embodiments, the heel side wing  660  extends perpendicularly from the rear periphery  652 , such that a right angle (90° angle) is formed at the junction of the heel side wing  660  and the rear periphery  652 . However, in other embodiments, the heel side wing  660  can extend from the rear periphery  652  in any direction, such that any angle)(0°-180° can be formed at the junction of the heel side wing  660  and the rear periphery  652 . 
     The front periphery  648 , of the lower portion  608 , comprises a front width. The front width is measured from the junction of the toe side wing  656  and the front periphery  648 , to the junction of the heel side wing  660  and the front periphery  648 . Further, the lower portion  608 , comprises a rear width. The rear width is measured from a tip  657  of the toe side wing  656  and a tip  661  of a toe side wing  660 , wherein the tip  657  is the point of the toe side wing  656  furthest from the front periphery  648  and the tip  661  is the point of the heel side wing  660  furthest from the front periphery  648 . In most embodiments, the front width is greater than the rear width, however in some embodiments, the front width can be equal to or less than the rear width. 
     The rear periphery  652 , toe side wing  656 , and heel side wing  660  form a gap  664 . The gap  664  is bounded by the rear periphery  652 , the toe side wing  656 , and the heel side wing  660 . The gap  664  formed by the rear periphery  652 , the toe side wing  656 , and the heel side wing  660  shifts a majority of the volume and mass of the putter to the extremities of the lower portion  608 . The gap  664  can comprise any shape, however in one embodiment the gap is approximately rectangular. In other embodiments, the gap  664  can be circular, curvilinear, triangular, trapezoidal, parabolic, golf ball shaped, square, or any other desired geometric shape. 
     The upper portion  604  of the putter head  600  comprises a toe end  612 , a heel end  616 , a strike face  620 , a rear wall  632 , a back edge  634 , a crown  642 , and an under surface (not pictured). The toe end  612  is opposite the heel end  616 . The strike face  620  spans from the toe end  612  to the heel end  616  and is opposite the rear wall  632 . The rear wall  632  is opposite, and approximately parallel to the strike face  620 . The crown  642  extends away from the strike face  620  and to the back edge  634  of the upper portion  604 . Furthermore, the under surface is opposite the crown  642 , spanning from the strike face  620  to the back edge  634 . 
     The crown  642  further descends from the strike face  620  to the back edge  634 . Additionally, the crown  642  extends away from the strike face  620 , over the front periphery  648  of lower portion  608 , and to the back edge  634  of the upper portion  604 . The crown  642 , in most embodiments, spans approximately inward 25% of the total club head  600  width from the toe side wing  656  and spans approximately inward 25% of the total club head  600  width from the heel side wing  660 . In other embodiments, the crown  642  can, continuously or discontinuously, span the entire width of the total club head  600 , in a heel to toe direction. In some embodiments, the crown  642 , can span less than 90% of the total width of the club head  600 , less than 90% of the total width of the club head  600 , less than 80% of the total width of the club head  600 , less than 70% of the total width of the club head  600 , less than 60% of the total width of the club head  600 , less than 50% of the total width of the club head  600 , less than 40% of the total width of the club head  600 , or less than 30% of the total width of the club head  600 . Further, in some embodiments, the crown  642  can be substantially flat from the strike face  620  to the back edge  634  or ascend from the strike face  620  to the back edge  634 . In most embodiments, the ascent or descent of the crown  642  can be linear, curvilinear, parabolic, sinusoidal, or a function of polynomial. 
     The crown  642  further comprises an alignment trough  655 , wherein the alignment trough  655  is equidistant from the heel end  616  and the toe end  612 . The alignment trough  655  is adjacent the rear wall  632  and approximately perpendicular to the strike face  620 . The alignment trough  655  is bounded by the back edge  634 , the rear wall  632 , and the crown  642  on the heel end  616  and the toe end  612 . In most embodiments, the alignment trough is approximately the width of a golf ball (approximately 4.27 cm) to provide the viewer a visual alignment field that extends the width of the golf ball. 
     Furthermore, the upper portion  604  of the putter head  600  can comprise one or more alignment features  644  on the crown  642 . The alignment feature  644  can be any one or combination of the following: a line, a series of lines, milling troughs, a circle, a dashed line, a triangle, a channel, or any other desired alignment feature  644 . The alignment features  644  can be equally spaced on the entire crown  642 , a portion of the crown  642 , or the alignment trough  655 . The alignment features  644 , extending along the alignment trough  655 , function to provide the viewer a visual alignment field that extends the width of the golf ball, from the rear wall  632  to the back edge  634  of the putter  600 . The goal is to align the entire putter  600  with the golf ball using these alignment features  644  along the crown  642  and/or the alignment trough  655 . 
     The upper portion  604  is affixed to the lower portion  608  such that the upper portion  604  is further from a ground plane  672  than the lower portion  608 , wherein the ground plane  672  is tangent to the lower portion  604 , when the putter head  600  is at an address position to strike a golf ball. 
     Further, the strike face  620  of the putter head  600  comprises a strike face center point  676  and a loft plane  680 . The strike face center point  676  is equidistant from the crown  642  and the undersurface of the upper portion  604 , as well as equidistant from the heel end  616  and toe end  612  of the putter head  600 . The loft plane  680  is tangent to the strike face  620  of the putter head  600 . Further, a midplane  684  intersects the strike face center point  676  and is perpendicular to the loft plane  680 . Furthermore, a y-axis  688  intersects the midplane  648 , and is perpendicular to the ground plane  672 . 
     When the upper portion  604  and lower portion  608  are joined such that the heel end  616  overlays at least a portion of the toe side wing  656 . Further, when the upper portion  604  and lower portion  608  are joined such that the toe end  612  overlays at least a portion of the heel side wing  660 . Further still, when the upper portion  604  and lower portion  608  are joined such that the strike face  620  overlays at least a portion of the front periphery  648 . Finally, the upper portion  604  and lower portion  608  are joined such that the back edge  634  overlays at least a portion of the rear periphery  652 . 
     Referring the  FIG. 6C , the front periphery  648 , rear periphery  652 , toe side wing  656 , and heel side wing  660  of the lower portion  608 , combined with the upper portion  604 , create a sole  668 . The sole  668  is perpendicular to the ground plane  672 , wherein the ground plane  672  is tangent to the sole  668 , when the putter head  600  is at an address position to strike a golf ball. The sole  668  of the putter head  600  extends from the toe end  612  of the putter head  600  to the heel end  616  of the putter head  600 . 
     In most embodiments, the sole  668  of the putter head  600  can be perfectly flat. In some embodiments, the sole  668  of the putter head  600  can have a slight arch in a heel  616  to toe  612  direction, wherein the slight arch can be linear, or a function of a polynomial. In some embodiments, the sole  668  of the putter head  600  can have a strong arch in the heel  616  to toe  612  direction, wherein the strong arch can be linear, or a function of a polynomial. The sole  668  functions to provide a surface to rest the putter head  600  on the ground plane  672 . 
     Referring to  FIG. 6A , in one embodiment, the lower portion  608  can further comprise a front toe mass  641 , a front heel mass  643 , a toe wing mass  645 , and a heel wing mass  647 . The front toe mass  641 , front heel mass  743 , toe wing mass  645 , and heel wing mass  647  are integral to the lower portion  608 . The front toe mass  641 , front heel mass  643 , toe wing mass  645 , and heel wing mass  647  extend from the lower portion  608 , in a direction away from the ground plane  672 , and toward the upper portion  604 . These mass portions provide a means to position to upper portion  604  and align with the lower portion  608  of the putter head  600 . Furthermore, these mass portions (i.e., the front toe mass  641 , front heel mass  643 , toe wing mass  645 , and heel wing mass  647 ) provide an additional means of adding weight to the perimeters for increasing the MOI of the putter  600  over putters without these mass features. These mass features can have weight that range from 2-5 grams, 3-7 grams or 1-6 grams. The mass features can have all the same weight or be different weight within the ranges provided above. The mass features can be 1 gram, 2 grams, 3 grams, 4 grams, 5 grams, 6 grams, or 7 grams. The front toe mass  641 , a front heel mass  643 , a toe wing mass  645 , and a heel wing mass  647  can respectively be any one or combination of the following shapes: rectangular, triangular, pyramidal, spherical, semi-circular, square, cylindrical, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     In one embodiment, the front toe mass  641  is positioned on the front periphery  648 , at the junction of the toe wing  656  and the front periphery  648 , however in other embodiments the front toe mass  641  can be positioned anywhere along the front periphery  648 . In one embodiment, the front heel mass  643 , is positioned on the front periphery  648 , at the junction of the heel wing  660  and the front periphery  648 , however in other embodiments the front heel mass  643  can be positioned anywhere along the front periphery  648 . In one embodiment, the toe wing mass  645  can be positioned over a portion of toe side wing  656 , however in other embodiments the toe wing mass  645  can be positioned anywhere along a portion of, or the entire, toe side wing  656 . In one embodiment, the heel wing mass  647  can be positioned over a portion of the heel side wing  660 , however in other embodiments the heel wing mass  647  can be positioned along a portion of, or the entire, heel side wing  660 . 
     The front toe mass  641 , front heel mass  643 , toe wing mass  645 , and heel wing mass  647 , provide areas of concentrated mass, such that each mass  641 ,  643 ,  645 , and  647  function to increase the moment of inertia of the putter head  600 . The placement of each mass  641 ,  643 ,  645 , and  647  on the periphery  648  and wings  656 ,  660 , increases the MOI since each mass  641 ,  643 ,  645 , and  647  since each mass is farther from a center of gravity of the putter  600 . Each mass  641 ,  643 ,  645 ,  647  on the periphery  648  and wings  656 ,  660  is integrally formed from the second material, wherein the second material is denser than the first material. 
     The front toe mass  641  and front heel mass  643  offer dual functionalities, such that the front toe mass  641  and front heel mass  643  function not only to increase the MOI of the putter  600  but provide additional surfaces for the upper portion  604  to join to the lower portion  608 . Therefore, the front toe mass  641  can also be referred to as a front toe adhesion portion  641  and the front heel mass  643  can also be referred to as a front heel adhesion portion  643 . 
     In some embodiments, the under surface, strike face  620 , and rear wall  632  of the upper portion  608 , can form a first cavity (not shown). The first cavity extends inwards from the under surface, on the toe end  612 , towards the crown  642  but does not reach the crown  642 . The first cavity is bounded by the rear wall  632 , the strike face  620 , and the toe  612 . The first cavity functions to receive the front toe mass  641  of the lower portion  608 . 
     In some embodiments, the under surface, strike face  620 , and rear wall  632  of the upper portion  608 , can form a second cavity (not shown). The second cavity extends inwards from the under surface, on the heel end  616 , towards the crown  642  but does not reach the crown  642 . The second cavity is bounded by the rear wall  632 , the strike face  620 , and the heel  616 . The second cavity functions to receive the front heel mass  643  of the lower portion  608 . 
     The first and second cavity can comprise any desired geometry, however in most embodiments, the first and second cavity comprise a geometry similar or identical to that of the front toe mass  641  and the front heel mass  643 . Further, when the upper portion  604  is affixed to the lower portion  608 , the first cavity is positioned such that the first cavity encompasses the front toe mass  641 , and the second cavity is positioned such that the second cavity encompasses the front heel mass  643 . 
     The combination of the low density first material upper portion  604  with the high density second material lower portion  608 , creates a high MOI putter  600 , without creating an extremely heavy putter. The large gap  664  formed by the rear periphery  652  and the wings  656 ,  660  of the lower portion  608  forms a dense, yet low volume portion that increases the MOI of the putter, in comparison to a putter milled from a single material. A single material putter fails to allocate high density material to the periphery, while maintaining a desirable volume (75 cc-100 cc) and mass (340 grams-385 grams). 
     The lower portion  608 , in most embodiments, comprises less than 38% of a total volume of the putter  600 . In some embodiments, the lower portion  608  comprises less than 37% of the total volume of the putter  600 , less than 36% of the total volume of the putter  600 , less than 35% of the total volume of the putter  600 , less than 34% of the total volume of the putter  600 , less than 33% of the total volume of the putter  600 , less than 32% of the total volume of the putter  600 , less than 31% of the total volume of the putter  600 , less than 30% of the total volume of the putter  600 , less than 29% of the total volume of the putter  600 , less than 28% of the total volume of the putter  600 , or less than 27% of the total volume of the putter  600 . 
     Although the lower portion  608  comprises less than half of the volume of the putter  600 , the lower portion  608  comprises at least 45% of an overall mass of the putter  600 . In some embodiments, the lower portion  608  comprises at least 46% of the overall mass of the putter  600 , at least 46% of the overall mass of the putter  600 , at least 47% of the overall mass of the putter  600 , at least 48% of the overall mass of the putter  600 , at least 49% of the overall mass of the putter  600 , at least 50% of the overall mass of the putter  600 , at least 51% of the overall mass of the putter  600 , at least 52% of the overall mass of the putter  600 , at least 53% of the overall mass of the putter  600 , at least 54% of the overall mass of the putter  600 , or at least 55% of the overall mass of the putter  600 . 
     The beneficial shift of mass to the periphery of the putter head  600 , through the use of a high density, low volume lower portion  608 , increases the MOI of the putter  600 , over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single stainless steel block, or a putter investment cast of a single material). 
     e. Spade Embodiment 
     In one embodiment, the putter-type golf club head can be a spade shaped putter head with periphery spans  700 . Referring to  FIGS. 7A and 7B , the spade shaped putter head  700  has a upper portion  704  and a lower portion  708 . The upper portion  704  is made from a first material have a first density and the lower portion  708  is made from a second material having a second density. The first density is less than the second density. The upper portion  704  and lower portion  708  combine to create a high-MOI putter head  700  (5000 gcm 2 -6500 gcm 2 ), while maintaining a desirable volume and mass. 
     As discussed above, the lower portion  708  is comprised of a high-density material (i.e., the first material), thereby lowering the mass below a midline  784 . The lower portion  708  comprises a front periphery  748 , a rear periphery  752 , a toe side periphery  756 , and a heel side periphery  760 . The front periphery  748  is adjacent to the toe side periphery  756  and the heel side periphery  760 , and opposite to the rear periphery  752 . The toe side periphery  756  is adjacent to the front periphery  748  and the rear periphery  752 , and opposite and to the heel side periphery  760 . The heel side periphery  760  is also adjacent to the front periphery  748  and the rear periphery  752 , but opposite to the toe side periphery  756 . In some embodiments, the heel side periphery  760  and toe side periphery  756  can be parallel, while in some embodiments the heel side periphery  760  and toe side periphery  756  are not parallel. In some embodiments, the rear periphery  752  and front periphery  748  can be parallel, while in some embodiments the rear periphery  752  and front periphery  748  are not parallel. 
     The front periphery  748 , of the lower portion  708 , comprises a front width. The front width is measured from the junction of the toe side periphery  756  and the front periphery  748 , to the junction of the heel side periphery  760  and the front periphery  748 . Further, the rear periphery  752 , of the lower portion  708 , comprises a rear width. The rear width is measured from the junction of the toe side periphery  756  and the rear periphery  752 , to the junction of the heel side periphery  760  and the rear periphery  752 . In most embodiments, the front width is greater than the rear width, however in some embodiments, the front width can be equal to or less than the rear width. 
     The front periphery  748 , rear periphery  752 , toe side periphery  756 , and heel side periphery  760 , join to from an aperture  764 , wherein the aperture  764  is bounded by the four peripheries (front  756 , rear  752 , toe side  756 , and heel side  760 ). The four peripheries  756 ,  752 ,  756 ,  760 , form a perimeter around the aperture  764 . The central aperture  764 , formed by the peripheries  756 ,  752 ,  756 ,  760  of the lower portion  708 , shifts a majority of the volume and mass of the putter to the extremities of the lower portion  708 . 
     The upper portion  704  of the putter head  700  comprises a toe end  712 , a heel end  716 , a strike face  720 , a rear wall  732 , a back edge  734 , a crown  742 , and an under surface (not pictured). The toe end  712  is opposite the heel end  716 . The strike face  720  spans from the toe end  712  to the heel end  716  and is opposite the rear wall  732 . The rear wall  732  is opposite, and approximately parallel to the strike face  720 . The crown  742  extends away from the strike face  720 , over at least a portion of the rear wall  732 , and to the back edge  734  of the upper portion  704 . Furthermore, the under surface is opposite the crown  742 , spanning from the strike face  720  to the back edge  734 . 
     The crown  742  further descends from the strike face  720  to the back edge  734 . Additionally, the crown  742  extends away from the strike face  720 , over at least a portion of the rear wall  732 , the aperture  764  of the lower portion  708 , and to the back edge  734  of the upper portion  704 . The crown  742 , in most embodiments, is inward 25% of the total club head  700  width from the toe side periphery  756  and the heel side periphery  760 . In this embodiment, the crown  742  spans approximately 50% of the width of the club head  700 . In other embodiments, the crown  742 , can span the entire width of the total club head  700 , in a heel to toe direction. In some embodiments, the crown  742 , can span less than 90% of the total width of the club head  700 , less than 90% of the total width of the club head  700 , less than 80% of the total width of the club head  700 , less than 70% of the total width of the club head  700 , less than 60% of the total width of the club head  700 , less than 50% of the total width of the club head  700 , less than 40% of the total width of the club head  700 , or less than 30% of the total width of the club head  700 . Further, in some embodiments, the crown  742  can be substantially flat from the strike face  720  to the back edge  734  or ascend from the strike face  720  to the back edge  734 . In most embodiments, the ascent or descent of the crown  742  can be linear, curvilinear, parabolic, sinusoidal, or a function of polynomial. 
     Furthermore, the upper portion  704  of the putter head  700  can comprise one or more alignment features  744  on the crown  742 . The alignment feature  744  can be any one or combination of the following: a line, a series of lines, milling troughs, a circle, a dashed line, a triangle, a channel, or any other desired alignment feature  744 . The alignment features  744  are equally spaced on the entire crown  742 , wherein the crown is configured to be the width of a golf ball (approximately 4.27 cm). The alignment features  744 , extending along the crown  742 , function to provide the viewer a visual alignment field that extends the width of the golf ball, from the strike face  720  to the back edge  734  of the putter  700 . The goal is to align the entire putter  700  with the golf ball using these alignment features  744  along the crown  742 . 
     Referring to  FIG. 7C , the upper portion  704  is affixed to the lower portion  708  such that the upper portion  704  is further from a ground plane  772  than the lower portion  708 , wherein the ground plane  772  is tangent to the lower portion  704 , when the putter head  700  is at an address position to strike a golf ball. 
     Further, the strike face  720  of the putter head  700  comprises a strike face center point  776  and a loft plane  780 . The strike face center point  776  is equidistant from the crown  742  and the undersurface of the upper portion  704 , as well as equidistant from the heel end  716  and toe end  712  of the putter head  700 . The loft plane  780  is tangent to the strike face  720  of the putter head  700 . Further, a midplane  748  intersects the strike face center point  776  and is perpendicular to the loft plane  780 . Furthermore, a y-axis  788  intersects the midplane  784 , and is perpendicular to the ground plane  772 . 
     When the upper portion  704  and lower portion  708  are joined such that the heel end  716  overlays at least a portion of the heel side periphery  760 . Further, when the upper portion  704  and lower portion  708  are joined such that the toe end  712  overlays at least a portion of the toe side periphery  756 . Further still, when the upper portion  704  and lower portion  708  are joined such that the strike face  720  overlays at least a portion of the front periphery  748 . Finally, the upper portion  704  and lower portion  708  are joined such that the back edge  734  overlays at least a portion of the rear periphery  752 . 
     Referring to  FIG. 7D , the four peripheries (front  748 , rear  752 , toe side  756 , and heel side  760 ) of the lower portion  708 , combined with the upper portion  704 , create a sole  768 . The sole  768  is perpendicular to the ground plane  772 , wherein the ground plane  772  is tangent to the sole  768 , when the putter head  700  is at an address position to strike a golf ball. The sole  768  of the putter head  700  extends from the toe end  712  of the putter head  700  to the heel end  716  of the putter head  700 . 
     In most embodiments, the sole  768  of the putter head  700  can be perfectly flat. In some embodiments, the sole  768  of the putter head  700  can have a slight arch in a heel  716  to toe  712  direction, wherein the slight arch can be linear, or a function of a polynomial. In some embodiments, the sole  768  of the putter head  700  can have a strong arch in the heel  716  to toe  712  direction, wherein the strong arch can be linear, or a function of a polynomial. The sole  768  functions to provide a surface to rest the putter head  700  on the ground plane  772 . 
     Referring to  FIG. 7A , in one embodiment, the lower portion  708  can further comprise a front mass  741 , a rear mass  743 , a toe mass  745 , and a heel mass  747 . The front mass  741 , rear mass  743 , toe mass  745 , and heel mass  747  are integral to the lower portion  708 . The front mass  741 , rear mass  743 , toe mass  745 , and heel mass  747  extend from the lower portion  708 , in a direction away from the ground plane  772 , and toward the upper portion  704 . These mass portions provide a means to position to upper portion  704  and align with the lower portion  708  of the putter head  700 . Furthermore, these mass portions (i.e., the front mass  741 , rear mass  743 , toe mass  745 , and heel mass  747 ) provide an additional means of adding weight to the perimeters for increasing the MOI of the putter  700  over putters without these mass features. These mass features can have weight that range from 2-5 grams, 3-7 grams or 1-6 grams. The mass features can have all the same weight or be different weight within the ranges provided above. The mass features can be 1 gram, 2 grams, 3 grams, 4 grams, 5 grams, 6 grams, or 7 grams. The front mass  741 , a rear mass  743 , a toe mass  745 , and a heel mass  747  can respectively be any one or combination of the following shapes: rectangular, triangular, pyramidal, spherical, semi-circular, square, cylindrical, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     In one embodiment, the front mass  741  is positioned on the front periphery  748 , is equidistance from the toe side periphery  756  and the heel side periphery  760 , however in other embodiments the front mass  741  can be positioned anywhere along the front periphery  748 . In one embodiment, the rear mass  743 , is positioned on the rear periphery  752 , equidistance from the toe side periphery  756  and the heel side periphery  760 , however in other embodiments the rear mass  743  can be positioned anywhere along the rear periphery  752 . In one embodiment, the toe mass  745  can be positioned at the junction of the toe side periphery  756  and the rear periphery  752 , however in other embodiments the toe mass  745  can be positioned anywhere along the toe side periphery  756 . In one embodiment, the heel mass  747  can be positioned at the junction of the heel side periphery  760  and the rear periphery  752 , however in other embodiments the heel mass  747  can be positioned anywhere along the heel side periphery  760 . 
     The front mass  741 , a rear mass  743 , a toe mass  745 , and a heel mass  747 , provide areas of concentrated mass, such that each mass  741 ,  743 ,  745 , and  747  function to increase the moment of inertia of the putter head  700 . The placement of each mass  741 ,  743 ,  745 , and  747  on the peripheries  748 ,  752 ,  756 ,  760 , increases the MOI since each mass  741 ,  743 ,  745 , and  747  since each mass is farther from a center of gravity of the putter  700 . Each mass  741 ,  743 ,  745 ,  747  on the peripheries  748 ,  752 ,  756 ,  760  is integrally formed from the second material, wherein the second material is denser than the first material. 
     The front mass  741  and the rear mass  743  offer dual functionalities, such that the front mass  741  and rear mass  743  function not only to increase the MOI of the putter  700  but provide additional surfaces for the upper portion  704  to join to the lower portion  708 . Therefore, the front mass  741  can also be referred to as a front adhesion portion  741  and the rear mass  743 . 
     In some embodiments, the under surface, strike face  720 , and rear wall  732  of the upper portion  708 , can form a first cavity (not shown). The first cavity extends inwards from the under surface towards the crown  742  but does not reach the crown  742 . The first cavity is bounded by the rear wall  732  and the strike face  720 . The first cavity functions to receive the front mass  741  of the lower portion  708 . 
     In some embodiments, the under surface, the back edge  734 , and the crown  742  forms a second cavity (not shown). The second cavity extends inwards from the under surface, towards the crown  742 , but does not reach the crown  742 . The second cavity is bounded by the back edge  734 , and the crown  732 . In most embodiments, the second cavity is positioned equidistance between the toe side periphery  756  and the heel side periphery  760 , when the lower portion  708  is joined to the upper portion  704 . The second cavity functions to receive the rear mass  743  of the lower portion  708 . 
     The first and second cavity can comprise any desired geometry, however in most embodiments, the first and second cavity comprise a geometry similar or identical to that of the front mass  741  and the rear mass  743 . Further, when the upper portion  704  is affixed to the lower portion  708 , the first cavity is positioned such that the first cavity encompasses the front mass  741 , and the second cavity is positioned such that the second cavity encompasses the rear mass  743 . 
     The combination of the low density first material upper portion  704  with the high density second material lower portion  708 , creates a high MOI putter  700 , without creating an extremely heavy putter. The large aperture  764  formed by the peripheries  748 ,  752 ,  756 ,  760  of the lower portion  708  forms a dense, yet low volume portion that increases the MOI of the putter, in comparison to a putter milled from a single material. A single material putter fails to allocate high density material to the periphery, while maintaining a desirable volume (75 cc-100 cc) and mass (340 grams-385 grams). 
     The lower portion  708 , in most embodiments, comprises less than 35% of a total volume of the putter  700 . In some embodiments, the lower portion  708  comprises less than 34% of the total volume of the putter  700 , less than 33% of the total volume of the putter  700 , less than 32% of the total volume of the putter  700 , less than 31% of the total volume of the putter  700 , less than 30% of the total volume of the putter  700 , less than 29% of the total volume of the putter  700 , less than 28% of the total volume of the putter  700 , or less than 27% of the total volume of the putter  700 . 
     Although the lower portion  708  comprises less than half of the volume of the putter  700 , the lower portion  708  comprises at least 45% of an overall mass of the putter  700 . In some embodiments, the lower portion  708  comprises at least 46% of the mass of the putter  700 , at least 47% of the mass of the putter  700 , at least 48% of the mass of the putter  700 , at least 49% of the mass of the putter  700 , at least 50% of the mass of the putter  700 , at least 51% of the mass of the putter  700 , at least 52% of the mass of the putter  700 , at least 53% of the mass of the putter  700 , at least 54% of the mass of the putter  700 , or at least 55% of the mass of the putter  700 . 
     The beneficial shift of mass to the periphery of the putter head  700 , through the use of a high density, low volume lower portion  708 , increases the MOI of the putter  700 , over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single stainless steel block, or a putter investment cast of a single material). 
     f. T-Shaped Embodiment with Periphery Spans 
     In one embodiment, the putter-type golf club head can be a T-shaped putter head with periphery spans  800 . Referring to  FIGS. 8A and 8B , the T-shaped putter head with periphery spans  800  has a upper portion  804  and a lower portion  808 . The upper portion  804  is made from a first material have a first density and the lower portion  808  is made from a second material having a second density. The first density is less than the second density. The upper portion  804  and lower portion  808  combine to create a high-MOI putter head  800  (5000 gcm 2 -6500 gcm 2 ), while maintaining a desirable volume and mass. 
     As discussed above, the lower portion  808  is comprised of a high-density material (i.e., the second material), thereby lowering the mass below a midline  884 . The lower portion  808  comprises a front periphery  848 , a rear periphery  852 , a toe side periphery  856 , and a heel side periphery  860 . The front periphery  848  is adjacent to the toe side periphery  856  and the heel side periphery  860 , and opposite to the rear periphery  852 . The toe side periphery  856  is adjacent to the front periphery  848  and the rear periphery  852 , and opposite and to the heel side periphery  860 . The heel side periphery  860  is also adjacent to the front periphery  848  and the rear periphery  852 , but opposite to the toe side periphery  856 . In some embodiments, the heel side periphery  860  and toe side periphery  856  can be parallel, while in some embodiments the heel side periphery  860  and toe side periphery  856  are not parallel. In some embodiments, the rear periphery  852  and front periphery  848  can be parallel, while in some embodiments the rear periphery  852  and front periphery  848  are not parallel. 
     The front periphery  848 , of the lower portion  808 , comprises a front width. The front width is measured from the junction of the toe side periphery  856  and the front periphery  848 , to the junction of the heel side periphery  860  and the front periphery  848 . Further, the rear periphery  852 , of the lower portion  808 , comprises a rear width. The rear width is measured from the junction of the toe side periphery  856  and the rear periphery  852 , to the junction of the heel side periphery  860  and the rear periphery  852 . In most embodiments, the front width is greater than the rear width, however in some embodiments, the front width can be equal to or less than the rear width. 
     The front periphery  848 , rear periphery  852 , toe side periphery  856 , and heel side periphery  860 , join to from an aperture  864 , wherein the aperture  864  is bounded by the four peripheries (front  856 , rear  852 , toe side  856 , and heel side  860 ). The four peripheries  856 ,  852 ,  856 ,  860 , form a perimeter around the aperture  864 . The central aperture  864 , formed by the peripheries  856 ,  852 ,  856 ,  860  of the lower portion  808 , shifts a majority of the volume and mass of the putter to the extremities of the lower portion  808 . 
     In some embodiments, the aperture  864 , formed by the front periphery  848 , rear periphery  852 , toe side periphery  856 , and heel side periphery  860  can be any one of the following shapes: rectangular, triangular, semi-circular, circular (golf ball sized), circular (larger than a golf ball), circular (smaller than a golf ball), square, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     The upper portion  804  of the putter head  800  comprises a toe end  812 , a heel end  816 , a strike face  820 , a rear wall  832 , a back edge  834 , a crown  842 , and an under surface (not pictured). The toe end  812  is opposite the heel end  816 . The strike face  820  spans from the toe end  812  to the heel end  816  and is opposite the rear wall  832 . The rear wall  832  is opposite, and approximately parallel to the strike face  820 . The crown  842  extends away from the strike face  820 , over at least a portion of the rear wall  832 , and to the back edge  834  of the upper portion  804 . Furthermore, the under surface is opposite the crown  842 , spanning from the strike face  820  to the back edge  834 . 
     The crown  842  further descends from the strike face  820  to the back edge  834 . Additionally, the crown  842  extends away from the strike face  820 , over at least a portion of the rear wall  832 , the aperture  864  of the lower portion  808 , and to the back edge  834  of the upper portion  804 . The crown  842 , in most embodiments, is inward 25% of the total club head  800  width from the toe side periphery  856  and the heel side periphery  860 . In this embodiment, the crown  842  spans approximately 50% of the width of the club head  800 , thus forming a “T-Shape” with the strike face. In other embodiments, the crown  842 , can span the entire width of the total club head  800 , in a heel to toe direction. In some embodiments, the crown  842 , can span less than 90% of the total width of the club head  800 , less than 90% of the total width of the club head  800 , less than 80% of the total width of the club head  800 , less than 70% of the total width of the club head  800 , less than 60% of the total width of the club head  800 , less than 50% of the total width of the club head  800 , less than 40% of the total width of the club head  800 , or less than 30% of the total width of the club head  800 . Further, in some embodiments, the crown  842  can be substantially flat from the strike face  820  to the back edge  834  or ascend from the strike face  820  to the back edge  834 . In most embodiments, the ascent or descent of the crown  842  can be linear, curvilinear, parabolic, sinusoidal, or a function of polynomial. 
     Furthermore, the upper portion  804  of the putter head  800  can comprise one or more alignment features  844  on the crown  842 . The alignment feature  844  can be any one or combination of the following: a line, a series of lines, milling troughs, a circle, a dashed line, a triangle, a channel, or any other desired alignment feature  844 . The alignment features  844  are equally spaced on the entire crown  842 , wherein the crown is configured to be the width of a golf ball (approximately 4.27 cm). The alignment features  844 , extending along the crown  842 , function to provide the viewer a visual alignment field that extends the width of the golf ball, from the strike face  820  to the back edge  834  of the putter  800 . The goal is to align the entire putter  800  with the golf ball using these alignment features  844  along the crown  842 . 
     Referring to  FIG. 8C , the upper portion  804  is affixed to the lower portion  808  such that the upper portion  804  is further from a ground plane  872  than the lower portion  808 , wherein the ground plane  872  is tangent to the lower portion  804 , when the putter head  800  is at an address position to strike a golf ball. 
     Further, the strike face  820  of the putter head  800  comprises a strike face center point  876  and a loft plane  880 . The strike face center point  876  is equidistant from the crown  842  and the undersurface of the upper portion  804 , as well as equidistant from the heel end  816  and toe end  812  of the putter head  800 . The loft plane  880  is tangent to the strike face  820  of the putter head  800 . Further, a midplane  884  intersects the strike face center point  876  and is perpendicular to the loft plane  880 . Furthermore, a y-axis  888  intersects the midplane  884 , and is perpendicular to the ground plane  872 . 
     When the upper portion  804  and lower portion  808  are joined such that the heel end  816  overlays at least a portion of the toe side periphery  856 . Further, when the upper portion  804  and lower portion  808  are joined such that the toe end  812  overlays at least a portion of the heel side periphery  860 . Further still, when the upper portion  804  and lower portion  808  are joined such that the strike face  820  overlays at least a portion of the front periphery  848 . Finally, the upper portion  804  and lower portion  808  are joined such that the back edge  834  overlays at least a portion of the rear periphery  852 . 
     Referring to  FIG. 8D , the four peripheries (front  848 , rear  852 , toe side  856 , and heel side  860 ) of the lower portion  808 , combined with the upper portion  804 , create a sole  868 . The sole  868  is perpendicular to the ground plane  872 , wherein the ground plane  872  is tangent to the sole  868 , when the putter head  800  is at an address position to strike a golf ball. The sole  868  of the putter head  800  extends from the toe end  812  of the putter head  800  to the heel end  816  of the putter head  800 . 
     In most embodiments, the sole  868  of the putter head  800  can be perfectly flat. In some embodiments, the sole  868  of the putter head  800  can have a slight arch in a heel  816  to toe  812  direction, wherein the slight arch can be linear, or a function of a polynomial. In some embodiments, the sole  868  of the putter head  800  can have a strong arch in the heel  816  to toe  812  direction, wherein the strong arch can be linear, or a function of a polynomial. The sole  868  functions to provide a surface to rest the putter head  800  on the ground plane  872 . 
     Referring to  FIG. 8A , in one embodiment, the lower portion  808  can further comprise a front mass  841 , a rear mass  843 , a toe mass  845 , and a heel mass  847 . The front mass  841 , rear mass  843 , toe mass  845 , and heel mass  847  are integral to the lower portion  808 . The front mass  841 , rear mass  843 , toe mass  845 , and heel mass  847  extend from the lower portion  808 , in a direction away from the ground plane  872 , and toward the upper portion  804 . These mass portions provide a means to position to upper portion  804  and align with the lower portion  808  of the putter head  800 . Furthermore, these mass portions (i.e., the front mass  841 , rear mass  843 , toe mass  845 , and heel mass  847 ) provide an additional means of adding weight to the perimeters for increasing the MOI of the putter  800  over putters without these mass features. These mass features can have weight that range from 2-5 grams, 3-7 grams or 1-6 grams. The mass features can have all the same weight or be different weight within the ranges provided above. The mass features can be 1 gram, 2 grams, 3 grams, 4 grams, 5 grams, 6 grams, or 7 grams. The front mass  841 , a rear mass  843 , a toe mass  845 , and a heel mass  847  can respectively be any one or combination of the following shapes: rectangular, triangular, pyramidal, spherical, semi-circular, square, cylindrical, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     In one embodiment, the front mass  841  is positioned on the front periphery  848 , is equidistance from the toe side periphery  856  and the heel side periphery  860 , however in other embodiments the front mass  841  can be positioned anywhere along the front periphery  848 . In one embodiment, the rear mass  843 , is positioned on the rear periphery  852 , equidistance from the toe side periphery  856  and the heel side periphery  860 , however in other embodiments the rear mass  843  can be positioned anywhere along the rear periphery  852 . In one embodiment, the toe mass  845  can be positioned at the junction of the toe side periphery  856  and the rear periphery  852 , however in other embodiments the toe mass  845  can be positioned anywhere along the toe side periphery  856 . In one embodiment, the heel mass  847  can be positioned at the junction of the heel side periphery  860  and the rear periphery  852 , however in other embodiments the heel mass  847  can be positioned anywhere along the heel side periphery  860 . 
     The front mass  841 , a rear mass  843 , a toe mass  845 , and a heel mass  847 , provide areas of concentrated mass, such that each mass  841 ,  843 ,  845 , and  847  function to increase the moment of inertia of the putter head  800 . The placement of each mass  841 ,  843 ,  845 , and  847  on the peripheries  848 ,  852 ,  856 ,  860 , increases the MOI since each mass  841 ,  843 ,  845 , and  847  since each mass is farther from a center of gravity of the putter  800 . Each mass  841 ,  843 ,  845 ,  847  on the peripheries  848 ,  852 ,  856 ,  860  is integrally formed from the second material, wherein the second material is denser than the first material. 
     The front mass  841  and the rear mass  843  offer dual functionalities, such that the front mass  841  and rear mass  843  function not only to increase the MOI of the putter  800  but provide additional surfaces for the upper portion  804  to join to the lower portion  808 . Therefore, the front mass  841  can also be referred to as a front adhesion portion  841  and the rear mass  843 . 
     In some embodiments, the under surface, strike face  820 , and rear wall  832  of the upper portion  808 , can form a first cavity (not shown). The first cavity extends inwards from the under surface towards the crown  842  but does not reach the crown  842 . The first cavity is bounded by the rear wall  832  and the strike face  820 . The first cavity functions to receive the front mass  841  of the lower portion  808 . 
     In some embodiments, the under surface, the back edge  834 , and the crown  842  forms a second cavity (not shown). The second cavity extends inwards from the under surface, towards the crown  842 , but does not reach the crown  842 . The second cavity is bounded by the back edge  834 , and the crown  832 . In most embodiments, the second cavity is positioned equidistance between the toe side periphery  856  and the heel side periphery  860 , when the lower portion  808  is joined to the upper portion  804 . The second cavity functions to receive the rear mass  843  of the lower portion  808 . 
     The first and second cavity can comprise any desired geometry, however in most embodiments, the first and second cavity comprise a geometry similar or identical to that of the front mass  841  and the rear mass  843 . Further, when the upper portion  804  is affixed to the lower portion  808 , the first cavity is positioned such that the first cavity encompasses the front mass  841 , and the second cavity is positioned such that the second cavity encompasses the rear mass  843 . 
     The combination of the low density first material upper portion  804  with the high density second material lower portion  808 , creates a high MOI putter  800 , without creating an extremely heavy putter. The large aperture  864  formed by the peripheries  848 ,  852 ,  856 ,  860  of the lower portion  808  forms a dense, yet low volume portion that increases the MOI of the putter, in comparison to a putter milled from a single material. A single material putter fails to allocate high density material to the periphery, while maintaining a desirable volume (75 cc-100 cc) and mass (340 grams-385 grams). 
     The lower portion  808 , in most embodiments, comprises less than 35% of a total volume of the putter  800 . In some embodiments, the lower portion  908  comprises less than 34% of the total volume of the putter  800 , less than 33% of the total volume of the putter  800 , less than 32% of the total volume of the putter  800 , less than 31% of the total volume of the putter  800 , less than 30% of the total volume of the putter  800 , less than 29% of the total volume of the putter  800 , less than 28% of the total volume of the putter  800 , or less than 27% of the total volume of the putter  800 . 
     Although the lower portion  808  comprises less than half of the volume of the putter  800 , the lower portion  808  comprises at least 45% of an overall mass of the putter  800 . In some embodiments, the lower portion  808  comprises at least 46% of the mass of the putter  800 , at least 46% of the mass of the putter  800 , at least 46% of the mass of the putter  800 , at least 47% of the mass of the putter  800 , at least 48% of the mass of the putter  800 , at least 49% of the mass of the putter  800 , at least 50% of the mass of the putter  800 , at least 51% of the mass of the putter  800 , at least 52% of the mass of the putter  800 , at least 53% of the mass of the putter  800 , at least 54% of the mass of the putter  800 , or at least 55% of the mass of the putter  800 . 
     The beneficial shift of mass to the periphery of the putter head  800 , through the use of a high density, low volume lower portion  808 , increases the MOI of the putter  800 , over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single stainless steel block, or a putter investment cast of a single material). 
     g. Dual-Rail Embodiment 
     In another embodiment, the putter-type golf club head can be a dual-rail putter head  900 . Referring to  FIGS. 9A and 9B , the dual-rail putter head  900  has a upper portion  904  and a lower portion  908 . The upper portion  904  is made from a first material have a first density and the lower portion  908  is made from a second material having a second density. The first density is less than the second density. The upper portion  904  and lower portion  908  combine to create a high-MOI putter head  900  (5000 gcm 2 -6500 gcm 2 ), while maintaining a desirable volume and mass. 
     As discussed above, the lower portion  908  is comprised of a high-density material (i.e., the second material), thereby lowering the mass below a midline  984 . The lower portion  908  comprises a front periphery  948 , a rear periphery  952 , a toe side periphery  956 , and a heel side periphery  960 . The front periphery  948  is adjacent to the toe side periphery  956  and the heel side periphery  960 , and opposite to the rear periphery  952 . The toe side periphery  956  is adjacent to the front periphery  948  and the rear periphery  952 , and opposite and to the heel side periphery  960 . The heel side periphery  956  is also adjacent to the front periphery  948  and the rear periphery  952 , but opposite to the toe side periphery  956 . In some embodiments, the heel side periphery  960  and toe side periphery  956  can be parallel, while in some embodiments the heel side periphery  960  and toe side periphery  956  are not parallel. In some embodiments, the rear periphery  952  and front periphery  948  can be parallel, while in some embodiments the rear periphery  952  and front periphery  948  are not parallel. 
     The front periphery  948 , of the lower portion  908 , comprises a front width. The front width is measured from the junction of the toe side periphery  956  and the front periphery  948 , to the junction of the heel side periphery  960  and the front periphery  948 . Further, the rear periphery  952 , of the lower portion  908 , comprises a rear width. The rear width is measured from the junction of the toe side periphery  956  and the rear periphery  952 , to the junction of the heel side periphery  960  and the rear periphery  952 . In most embodiments, the front width is greater than the rear width, however in some embodiments, the front width can be equal to or less than the rear width. 
     The front periphery  948 , rear periphery  952 , toe side periphery  956 , and heel side periphery  960 , join to from an aperture  964 , wherein the aperture  964  is bounded by the four peripheries (front  948 , rear  952 , toe side  956 , and heel side  960 ). The four peripheries  948 ,  952 ,  956 ,  960 , form a perimeter around the aperture  964 . The central aperture  964 , formed by the peripheries  948 ,  952 ,  956 ,  960  of the lower portion  908 , shifts a majority of the volume and mass of the putter to the extremities of the lower portion  908 . 
     In some embodiments, the aperture  964 , formed by the front periphery  948 , rear periphery  952 , toe side periphery  956 , and heel side periphery  960  can be any one of the following shapes: rectangular, triangular, semi-circular, circular (golf ball sized), circular (larger than a golf ball), circular (smaller than a golf ball), square, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     The upper portion  904  of the dual-rail putter head  900  comprises a toe end  912 , a heel end  916 , a strike face  920 , a rear wall  932 , a back edge  934 , a crown  942 , and an under surface (not pictured). The toe end  912  is opposite the heel end  916 . The strike face  920  spans from the toe end  912  to the heel end  916  and is opposite the rear wall  932 . The rear wall  932  is opposite, and approximately parallel to the strike face  920 . The crown  942  extends away from the strike face  920 , over at least a portion of the rear wall  932 , and to the back edge  934  of the upper portion  904 . Furthermore, the under surface is opposite the crown  942 , spanning from the strike face  920  to the back edge  934 . 
     The crown  942  of the upper portion  904  further comprises a toe end mid-rail  936  and a heel end mid-rail  940 . In most embodiments, the toe end mid-rail  936  and heel end mid-rail  940  are approximately parallel, while perpendicular to the strike face  920 . Further, the toe end mid-rail  936  and heel end mid-rail  940  do not contact the toe side periphery  956  or the heel side periphery  960 . The toe end mid-rail  936  and the heel end mid-rail  940  are approximately ⅓ inward of the total club head width from the outer periphery of the toe side periphery  956  and heel side periphery  960  respectively. However, in other embodiments, the toe end mid-rail  936  and the heel end mid-rail  940  can be more or less than ⅓ inward of the total club head width from the outer periphery of the toe-side periphery and heel-side periphery respectively. The toe end mid-rail  936  and heel end mid-rail  940  descend from the strike face  920  to the back edge  934 . In some embodiments, the toe end mid-rail  936  and heel end mid-rail  940  are not parallel and not perpendicular to the strike face  920 . In some embodiments, the toe end mid-rail  936  and heel end mid-rail  940  can be substantially flat from the strike face  920  to the back edge  934  or ascend from the strike face  920  to the back edge  934 . In most embodiments, the ascent or descent of the mid-rails  936 ,  940  can be linear, curvilinear, parabolic, sinusoidal, or a function of polynomial. 
     Furthermore, the upper portion  904  of the dual-rail putter head  900  can comprise one or more alignment features  944  on toe end mid-rail  936  and heel end mid-rail  940 . The alignment feature  944  can be any one or combination of the following: a line, a circle, a dashed line, a triangle, a channel, or any other desired alignment feature  944 . The alignment features  944  are spaced such on the rails  936 ,  940  to be the width of a golf ball (approximately 4.27 cm). The alignment features  944  extend along the rails to provide the viewer a visual alignment field that extends from the golf ball, strike face  920  to the entire putter  900 . The goal is to align the entire putter  900  with the golf ball using these alignment features  944  along the toe end mid-rail  936  and heel end mid-rail  940 . 
     The upper portion  904  is affixed to the lower portion  908  such that the upper portion  904  is further from a ground plane  972  than the lower portion  908 , wherein the ground plane  972  is tangent to the lower portion  904 , when the dual-rail putter head  900  is at an address position to strike a golf ball. 
     Further, the strike face  920  of the dual-rail putter head  900  comprises a strike face center point  976  and a loft plane  980 . The strike face center point  976  is equidistant from the crown  942  and the undersurface of the upper portion  904 , as well as equidistant from the heel end  916  and toe end  912  of the dual-rail putter head  900 . The loft plane  980  is tangent to the strike face  920  of the dual-rail putter head  900 . Further, a midplane  984  intersects the strike face center point  976  and is perpendicular to the loft plane  980 . Furthermore, a y-axis  988  intersects the midplane  984 , and is perpendicular to the ground plane  972 . 
     When the upper portion  904  and lower portion  908  are joined such that the heel end  916  overlays at least a portion of the toe side periphery  956 . Further, when the upper portion  904  and lower portion  908  are joined such that the toe end  912  overlays at least a portion of the heel side periphery  960 . Further still, when the upper portion  904  and lower portion  908  are joined such that the strike face  920  overlays at least a portion of the front periphery  948 . Finally, when the upper portion  904  and lower portion  908  are joined such that the back edge  934  overlays at least a portion of the rear periphery  952 . 
     Referring to  FIGS. 9C and 9D , the four peripheries (front  948 , rear  952 , toe side  956 , and heel side  960 ) of the lower portion  908 , combined with the upper portion  904 , create a sole  968 . The sole  968  is perpendicular to the ground plane  972 , wherein the ground plane  972  is tangent to the sole  968 , when the dual-rail putter head  900  is at an address position to strike a golf ball. The sole  968  of the dual-rail putter head  900  extends from the toe end  912  of the dual-rail putter head  900  to the heel end  916  of the dual-rail putter head  900 . 
     In most embodiments, the sole  968  of the dual-rail putter head  900  can be perfectly flat. In some embodiments, the sole  968  of the putter head  900  can have a slight arch in a heel to toe direction, wherein the slight arch can be linear, or a function of a polynomial. In some embodiments, the sole  968  of the putter head  900  can have a strong arch in the heel to toe direction, wherein the strong arch can be linear, or a function of a polynomial. The sole  968  functions to provide a surface to rest the dual-rail putter head  900  on the ground plane  972 . 
     Referring to  FIG. 9A , in one embodiment, the lower portion  908  can further comprise a front mass  941 , a rear mass  943 , a toe mass  945 , and a heel mass  947 . The front mass  941 , rear mass  943 , toe mass  945 , and heel mass  947  are integral to the lower portion  908 . The front mass  941 , rear mass  943 , toe mass  945 , and heel mass  947  extend from the lower portion  908 , in a direction away from the ground plane  972 , and toward the upper portion  904 . These mass portions provide a means to position to upper portion and align with the lower portion of the dual-rail putter head  900 . Furthermore, these mass portions (i.e., the front mass  941 , rear mass  943 , toe mass  945 , and heel mass  947 ) provide an additional means of adding weight to the perimeters for increasing the MOI of the putter over putters without these mass features. These mass features can have weight that range from 2-5 grams, 3-7 grams or 1-6 grams. The mass features can have all the same weight or be different weight within the ranges provided above. The mass features can be 1 gram, 2 grams, 3 grams, 4 grams, 5 grams, 6 grams, or 7 grams. The front mass  941 , a rear mass  943 , a toe mass  945 , and a heel mass  947  can respectively be any one or combination of the following shapes: rectangular, triangular, pyramidal, spherical, semi-circular, square, cylindrical, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     In one embodiment, the front mass  941  is positioned on the front periphery  948 , is equidistance from the toe side periphery  956  and the heel side periphery  960 , however in other embodiments the front mass  941  can be positioned anywhere along the front periphery  948 . In one embodiment, the rear mass  943 , is positioned on the rear periphery  952 , equidistance from the toe side periphery  956  and the heel side periphery  960 , however in other embodiments the rear mass  943  can be positioned anywhere along the rear periphery  952 . In one embodiment, the toe mass  945  can be positioned at the junction of the toe side periphery  956  and the rear periphery  952 , however in other embodiments the toe mass  945  can be positioned anywhere along the toe side periphery  956 . In one embodiment, the heel mass  947  can be positioned at the junction of the heel side periphery  960  and the rear periphery  952 , however in other embodiments the heel mass  947  can be positioned anywhere along the heel side periphery  960 . 
     The front mass  941 , a rear mass  943 , a toe mass  945 , and a heel mass  947 , provide areas of concentrated mass, such that each mass  941 ,  943 ,  945 , and  947  function to increase the moment of inertia of the putter head  900 . The placement of each mass  941 ,  943 ,  945 , and  947  on the peripheries  948 ,  952 ,  956 ,  960 , increases the MOI since each mass  941 ,  943 ,  945 , and  947  since each mass is farther from a center of gravity of the putter  900 . Each mass  941 ,  943 ,  945 ,  947  on the peripheries  948 ,  952 ,  956 ,  960  is integrally formed from the second material, wherein the second material is denser than the first material. 
     The front mass  941 , a rear mass  943 , a toe mass  945 , and a heel mass  947  offer dual functionalities, such that each mass  941 ,  943 ,  945 , and  947  functions not only to increase the MOI of the putter  900 , but provide additional surface for the upper portion  904  to join to the lower portion  908 . Therefore, the front mass  941  can also be referred to as a front adhesion portion  941 , the rear mass  943  can also be referred to as rear adhesion portion  943 , the toe mass  945  can also be referred to as a toe adhesion portion  945 , and the heel mass  947  can also be referred to as a heel adhesion portion  947 . 
     Further, the crown  942  of the upper portion  942  comprises a toe end cap  949 , and a heel end cap  951 , such that the toe end cap  949  and heel end cap  951  function to mate to the toe mass  945  and the heel mass  947 , respectively. The toe end cap  949  is adjacent the toe end mid-rail  936  and the back edge  934 . The heel end cap  951  is adjacent the heel end mid-rail  940  and the back edge  934 . In most embodiments, the toe end cap  949  and heel end cap  951  comprise identical geometries, however in some embodiments, the toe end cap  949  and heel end cap  951  can comprise different geometries. 
     In most embodiments, the toe end cap  949  and heel end cap  951 , of the crown  942 , are larger than the toe mass  945  and heel mass  947 , respectively, so that the toe end cap  949  and heel end cap  951  encompass the toe mass  945  and heel mass  947 , when the upper portion  904  is affixed to the lower portion  908 . Further, when the upper portion  904  is affixed to the lower portion  908 , the toe end cap  949  is positioned such that the toe end cap  949  overlays at least a portion of the toe side periphery  956  and the toe mass  945 . Further still, when the upper portion  904  is affixed to the lower portion  908 , the heel end cap  951  is positioned such that the heel end cap  951  overlays at least a portion of the heel side periphery  960  and the heel mass  960 . 
     In some embodiments, the under surface, strike face  920 , and rear wall  932  of the upper portion  908 , can form a first cavity (not shown). The first cavity extends inwards from the under surface towards the crown  942  but does not reach the crown  942 . The first cavity is bounded by the rear wall  932  and the strike face  920 . The first cavity functions to receive the front mass  941  of the lower portion  908 . 
     In some embodiments, the under surface, the back edge  934 , and the crown  942  forms a second cavity (not shown). The second cavity extends inwards from the under surface, towards the crown  942 , but does not reach the crown  942 . The second cavity is bounded by the back edge  934 , the toe cap  949 , and the heel end cap  951 . In most embodiments, the second cavity is positioned equidistance between the toe end cap  949  and the heel end cap  951 . The second cavity functions to receive the rear mass  943  of the lower portion  908 . 
     The first and second cavity can comprise any desired geometry, however in most embodiments, the first and second cavity comprise a geometry similar or identical to that of the front mass  941  and the rear mass  943 . Further, when the upper portion  904  is affixed to the lower portion  908 , the first cavity is positioned such that the first cavity encompasses the front mass  941 , and the second cavity is positioned such that the second cavity encompasses the rear mass  943 . 
     The combination of the low density first material upper portion  904  with the high density second material lower portion  908 , creates a high MOI putter  900 , without creating an extremely heavy putter. The large aperture  964  formed by the peripheries  948 ,  952 ,  956 ,  960  of the lower portion  908  forms a dense, yet low volume portion that increases the MOI of the putter, in comparison to a putter milled from a single material. A single material putter fails to allocate high density material to the periphery, while maintaining a desirable volume (75 cc-100 cc) and mass (340 grams-385 grams). 
     The lower portion  908 , in most embodiments, comprises less than 35% of a total volume of the putter  900 . In some embodiments, the lower portion  908  comprises less than 34% of the total volume of the putter  900 , less than 33% of the total volume of the putter  900 , less than 32% of the total volume of the putter  900 , less than 31% of the total volume of the putter  900 , less than 30% of the total volume of the putter  900 , less than 29% of the total volume of the putter  900 , less than 28% of the total volume of the putter  900 , or less than 27% of the total volume of the putter  900 . 
     Although the lower portion  908  comprises less than half of the volume of the putter  900 , the lower portion  908  comprises at least 45% of an overall mass of the putter  900 . In some embodiments, the lower portion  908  comprises at least 46% of the mass of the putter  900 , at least 46% of the mass of the putter  900 , at least 46% of the mass of the putter  900 , at least 47% of the mass of the putter  900 , at least 48% of the mass of the putter  900 , at least 49% of the mass of the putter  900 , at least 50% of the mass of the putter  900 , at least 51% of the mass of the putter  900 , at least 52% of the mass of the putter  900 , at least 53% of the mass of the putter  900 , at least 54% of the mass of the putter  900 , or at least 55% of the mass of the putter  900 . 
     The beneficial shift of mass to the periphery of the putter head  900 , through the use of a high density, low volume lower portion  908 , increases the MOI of the putter  900 , over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single stainless steel block, or a putter investment cast of a single material). 
     h. Circular Embodiment 
     In another embodiment, the putter-type golf club head  1000  can be a circular shaped putter head  1000 . Referring to  FIG. 10A-10C , the circular putter head  1000  has an upper portion  1004  and a lower portion  1008 . The lower portion  1008  is made from a first material have a first density and the upper portion  1004  is made from a second material having a second density. The first density is less than the second density. The upper portion  1004  and lower portion  1008  combine to create a high-MOI putter head  1000  (5000 g·cm 2 -6500 g·cm 2 ), while maintaining a desirable volume and mass. 
     As discussed above, the upper portion  1004  is comprised of a high-density material (i.e., the second material). The upper portion  1004  comprises a toe end  1012 , a heel end  1016 , a strike face  1020 , a rear wall  1032 , and an under surface (not pictured). The toe end  1012  is opposite the heel end  1016 . The strike face  1020  spans from the toe end  1012  to the heel end  1016  and is opposite the rear wall  1032 . The rear wall  1032  is opposite, and approximately parallel to the strike face  1020 . 
     The upper portion  1004  further comprises a toe side span  1056 , and a heel side span  1060 . The toe side span  1056  is adjacent to the toe end  1012  and opposite and to the heel side span  1060 . The heel side span  1060  is also adjacent to the heel end  1016  and opposite to the toe side span  1056 . In some embodiments, the heel side span  1060  and toe side span  1056  can be parallel, while in some embodiments, the heel side span  1060  and toe side span  1056  are not parallel. The toe side span  1056  and heel side span  1060 , extend perpendicularly away from the rear wall  1032 , in a direction away from the rear wall  1032 , and strike face  1020 . 
     In most embodiments, the toe side span  1056  extends perpendicularly from rear wall  1032  such that a right angle (90° angle) is formed at the junction of the toe side span  1056  and the rear wall  1032 . However, in other embodiments, the toe side span  1056  can extend from the rear wall  1032  in any direction, such that any angle)(0°-180° can be formed at the junction of the toe side span  1056  and the rear wall  1032 . Further, in most embodiments, the heel side span  1060  extends perpendicularly from the rear wall  1032 , such that a right angle (90° angle) is formed at the junction of the heel side span  1060  and the rear wall  1032 . However, in other embodiments, the heel side span  1060  can extend from the rear wall  1032  in any direction, such that any angle) (0°-180° can be formed at the junction of the heel side span  1060  and the rear wall  1032 . 
     The rear wall  1032 , toe side span  1056 , and heel side span  1060  form a gap  1064 . The gap  1064  is bounded by the rear wall  1032 , the toe side span  1056 , and the heel side span  1060 . The gap  1064  formed by the rear wall  1032 , the toe side span  1056 , and the heel side span  1060  shifts a majority of the volume and mass of the putter to the extremities of the upper portion  1008 . The gap  1064  can comprise any shape, however in one embodiment the gap is approximately rectangular. In other embodiments, the gap  1064  can be circular, curvilinear, triangular, trapezoidal, parabolic, golf ball shaped, square, or any other desired geometric shape. 
     The lower portion  1008  of the putter head  1000  comprises a front edge  1041 , a rear edge  1034 , a toe edge  1043 , and a heel edge  1045 . The front edge  1041  is adjacent to the toe edge  1043  and the heel edge  1045 , and opposite to the rear edge  1034 . The toe edge  1034  is adjacent to the front edge  1041  and rear edge  1034 , and opposite to the heel edge  1045 . The heel edge  1045  is also adjacent to the front edge  1041  and the rear edge  1034 , and opposite to the toe edge  1043 . In some embodiments, the toe edge  1043  and heel edge  1045  can be parallel, while in some embodiments, the toe edge  1043  and heel edge  1045  are not parallel. In some embodiments, the front edge  1041  and rear edge  1034  can be parallel, while in some embodiments, the front edge  1041  and rear edge  1034  are not parallel. 
     The front edge  1041 , rear edge  1034 , toe edge  1043 , and heel edge  1045  join to form an aperture  1065 , wherein the aperture  1065  is bounded by the four edges (front  1041 , rear  1034 , toe  1043 , heel  1045 ). The four edges  1041 ,  1034 ,  1043 ,  1045 , form a perimeter around the aperture  1065 . 
     In some embodiments, the aperture  1065 , formed by the front edge  1041 , rear edge  1034 , toe edge  1043 , and heel edge  1045  can be any one of the following shapes: rectangular, triangular, semi-circular, circular (golf ball sized), circular (larger than a golf ball), circular (smaller than a golf ball), square, ovular, elliptical, trapezoidal, pentagonal, hexagonal, octagonal, or any other desired geometric or non-geometric shape. 
     Referring to  FIG. 10C , the lower portion  1008  is affixed to the upper portion  1004  such that a portion of the upper portion  1004  and the lower portion  1008  intersect a ground plane  1072 . The ground plane  1072  is tangent to the lower portion  1004 , when the putter head  1000  is at an address position to strike a golf ball. 
     Further, the strike face  1020  of the putter head  1000  comprises a strike face center point  1076  and a loft plane  1080 . The strike face center point  1076  is equidistant from a top rail  1050  and the ground plane  1072  of the upper portion  1004 , wherein the top rail  1050  is adjacent the strike face  1020  and the rear wall  1032 , while opposite the ground plane  1072 . The strike face center point  1076  is also equidistant from the heel end  1016  and toe end  1012  of the putter head  1000 . The loft plane  1080  is tangent to the strike face  1020  of the putter head  1000 . Further, a midplane  1084  intersects the strike face center point  1076  and is perpendicular to the loft plane  1080 . Furthermore, a y-axis  1088  intersects the midplane  1084 , and is perpendicular to the ground plane  1072 . 
     When the upper portion  1004  and lower portion  1008  are joined such that the toe side span  1056  overlays at least a portion of the toe edge  1043 . Further, when the upper portion  1004  and lower portion  1008  are joined such that the heel side span  1060  overlays at least a portion of the heel edge  1045 . Further still, when the upper portion  1004  and lower portion  1008  are joined such that the strike face  1020  overlays at least a portion of the front edge  1048 . Finally, when the upper portion  1004  and lower portion  1008  are joined such that the lower portion  1008  is affixed to a portion of the strike face  1020 , toe side span  1056 , and heel side span  1060 , thereby filling at least a portion of the gap  1064  formed by the rear wall  1032 , toe side span  1056 , and heel side span  1060   
     Referring to  FIG. 10D  the lower portion  1008 , and the toe side span  1056  and heel side span  1060  of the upper portion  1004 , when combined create a sole  1068 . The sole  1068  is perpendicular to the ground plane  1072 , wherein the ground plane  1072  is tangent to the sole  1068 , when the putter head  1000  is at an address position to strike a golf ball. The sole  1068  of the putter head  1000  extends from the toe end  1012  of the putter head  1000  to the heel end  1016  of the putter head  1000 . 
     In most embodiments, the sole  1068  of the putter head  1000  can be perfectly flat. In some embodiments, the sole  1068  of the putter head  1000  can have a slight arch in a heel  1016  to toe  1012  direction, wherein the slight arch can be linear, or a function of a polynomial. In some embodiments, the sole  1068  of the putter head  1000  can have a strong arch in the heel  1016  to toe  1012  direction, wherein the strong arch can be linear, or a function of a polynomial. The sole  1068  functions to provide a surface to rest the putter head  1000  on the ground plane  1072 . 
     In some embodiments, the upper portion  1004  can further comprise a crown (not shown). The crown extends away from the strike face  1020  to the back edge  1034  of the lower portion  1008 . Furthermore, the crown, spans from the strike face  1020  to the back edge  1034 , at least over a portion of the aperture  1065  of the lower portion and at least over a portion of the rear wall  1032 . 
     The crown can further descend from the strike face  1020  to the back edge  1034 . The crown, in most embodiments, spans approximately inward 25% of the total club head  1000  width from the toe side span  1056  and spans approximately inward 25% of the total club head  1000  width from the heel side span  1060 . In other embodiments, the crown can, continuously or discontinuously, span the entire width of the total club head  1000 , in a heel to toe direction. In some embodiments, the crown, can span less than 90% of the total width of the club head  1000 , less than 90% of the total width of the club head  1000 , less than 80% of the total width of the club head  1000 , less than 70% of the total width of the club head  1000 , less than 60% of the total width of the club head  1000 , less than 50% of the total width of the club head  1000 , less than 40% of the total width of the club head  1000 , or less than 30% of the total width of the club head  1000 . Further, in some embodiments, the crown can be substantially flat from the strike face  1020  to the back edge  1034  or ascend from the strike face  1020  to the back edge  1034 . In most embodiments, the ascent or descent of the crown can be linear, curvilinear, parabolic, sinusoidal, or a function of polynomial. 
     Furthermore, the upper portion  1004  of the putter head  1000  can comprise one or more alignment features  1044  on the toe side span  1065  and the heel side span  1060 . The alignment feature  1044  can be any one or combination of the following: a line, a series of lines, milling troughs, a circle, a dashed line, a triangle, a channel, or any other desired alignment feature  1044 . The alignment features  1044  can be equally spaced on the entire toe side span  1065  and the heel side span  1060 , a portion of the crown, or the entire crown. The alignment features  1044 , extending along the toe side span  1056  and the heel side span  1060 , function to provide the viewer a visual alignment field that extends the width of the golf ball, from the rear wall  1032  to the back edge  1034  of the putter  1000 . The goal is to align the entire putter  1000  with the golf ball using these alignment features  1044  along the toe side span  1056  and the heel side span  1060  and/or the crown. 
     The combination of the high density first material upper portion  1004  with the low density second material lower portion  1008 , creates a high MOI putter  1000 , without creating an extremely heavy putter. The large gap  1064  formed by the rear wall  1032  and the spans  1056 ,  1060  of the upper portion  1004  forms a dense, yet low wide periphery that increases the MOI of the putter, in comparison to a putter milled from a single material. A single material putter fails to allocate high density material to the periphery, while maintaining a desirable volume (75 cc-100 cc) and mass (340 grams-385 grams). 
     The beneficial shift of mass to the periphery of the putter head  1000 , through the use of a high density, upper portion  1008 , and low volume low mass lower portion  100 , increases the MOI of the putter  1000 , over a putter with the same volume, mass, and single material construction (i.e., a putter milled of a single stainless steel block, or a putter investment cast of a single material). 
     Replacement of one or more claimed elements constitutes reconstruction and not repair. Additionally, benefits, other advantages, and solutions to problems have been described with regard to specific embodiments. The benefits, advantages, solutions to problems, and any element or elements that may cause any benefit, advantage, or solution to occur or become more pronounced, however, are not to be construed as critical, required, or essential features or elements of any or all of the claims. 
     As the rules to golf may change from time to time (e.g., new regulations may be adopted or old rules may be eliminated or modified by golf standard organizations and/or governing bodies such as the United States Golf Association (USGA), the Royal and Ancient Golf Club of St. Andrews (R&amp;A), etc.), golf equipment related to the apparatus, methods, and articles of manufacture described herein may be conforming or non-conforming to the rules of golf at any particular time. Accordingly, golf equipment related to the apparatus, methods, and articles of manufacture described herein may be advertised, offered for sale, and/or sold as conforming or non-conforming golf equipment. The apparatus, methods, and articles of manufacture described herein are not limited in this regard. 
     The above examples may be described in connection with a putter-type golf club, the apparatus, methods, and articles of manufacture described herein. Alternatively, the apparatus, methods, and articles of manufacture described herein may be applicable other type of sports equipment such as a hockey stick, a tennis racket, a fishing pole, a ski pole, etc. 
     Moreover, embodiments and limitations disclosed herein are not dedicated to the public under the doctrine of dedication if the embodiments and/or limitations: (1) are not expressly claimed in the claims; and (2) are or are potentially equivalents of express elements and/or limitations in the claims under the doctrine of equivalents. 
     Clause 1: A putter type golf club head comprising: an upper portion and a lower portion; wherein the upper portion is made from a first material having a first density and the lower portion is made from a second material having a second density; wherein the first density is less than the second density; the lower portion comprises a front periphery, a toe side periphery, a heel side periphery, and a rear periphery; wherein the lower portion further comprises an aperture bounded by the front periphery, toe side periphery, heel side periphery, and rear periphery; the upper portion comprises a heel end, a toe end, a strike face, a rear wall, a back edge, a crown, and an under surface; wherein the toe end is opposite the heel end, the back edge is opposite the strike face; the crown extends away from the strike face, over at least a portion of the rear wall, and to the back edge; the under surface is opposite the crown spanning from the strike face to the back edge; the upper portion is affixed to the lower portion, and is farther from a ground plane than the lower portion, wherein the heel end overlays at least a portion of the heel side periphery, the toe end overlays at least a portion of the toe side periphery, the strike face overlays at least a portion of the front periphery, and the crown spans from the strike face to the rear periphery; the lower portion and upper portion combine to create a sole; wherein the sole is tangent to the ground plane, when the golf club head is at an address position; the strike face is tangent to a loft plane, wherein a loft angle formed between the loft plane and the ground plane; a volume and a mass; wherein the lower portion comprises less than 30% of the volume of the golf club head; and wherein the lower portion comprises greater than 50% of the mass of the golf club head. 
     Clause 2: The putter type golf club head of clause 1, wherein the lower portion further comprises: a toe mass at the junction of the toe side periphery and the rear periphery; a heel mass at the junction of the heel side periphery and the rear periphery; a rear mass positioned on the rear periphery, equidistance from the toe side periphery and the heel side periphery; and a front mass positioned on the front periphery, equidistance from the toe side periphery and the heel side periphery. 
     Clause 3: The putter type golf club head of clause 2, wherein the toe mass, heel mass, rear mass, and front mass are integral and extend away from the lower portion, in a direction away from the ground plane and toward the upper portion. 
     Clause 4: The putter type golf club head of clause 1, wherein the crown, of the upper portion, further comprises a toe end mid-rail, a heel end mid-rail, a toe end cap, and a heel end cap. 
     Clause 5: The putter type golf club head of clause 4, wherein the toe end cap is configured to mate with the toe mass and the heel end cap is configured to mate with the heel mass. 
     Clause 6: The putter type golf club head of clause 5, wherein the upper portion further comprises a first cavity, wherein the first cavity is formed in the under surface, between the strike face and the rear wall, and extends in a direction towards the crown; and a second cavity, wherein the rear aperture is formed in the under surface, adjacent the back edge, and equidistant between the toe end cap and the heel end cap. 
     Clause 7: The putter type golf club head of clause 6, wherein the first cavity is configured to mate with the front mass, and the second cavity is configured to mate with the rear mass. 
     Clause 8: The putter type golf club head of clause 4, wherein the toe end mid-rail and heel end mid-rail descend from the strike face to the rear periphery. 
     Clause 9: The putter type golf club head of clause 4, wherein the heel end mid-rail and the toe end mid-rail comprise one or more alignment features on the heel end mid-rail and the toe end mid-rail. 
     Clause 10: The putter type golf club head of clause 9, wherein the one or more alignment features can be unequally or equally spaced apart from the strike face to the rear periphery. 
     Clause 11: The putter type golf club head of clause 1, wherein the front periphery, of the lower portion, comprises a front width measured from the junction of the toe side periphery and the front periphery, to the junction of the heel side periphery and the front periphery; 
     Clause 12: The putter type golf club head of clause 11, wherein the rear periphery, of the lower portion, comprises a rear width measured from the junction of the toe side periphery and the rear periphery, to the junction of the heel side periphery and the rear periphery. 
     Clause 13: The putter type golf club head of clause 12, wherein the front width is greater than the rear width. 
     Clause 14: The putter type golf club head of clause 1, wherein one or more alignment feature is positioned on the crown. 
     Clause 15: The putter type golf club head of clause 1, wherein the first density of the first material is less than 6.0 g/cc. 
     Clause 16: The putter type golf club head of clause 1, wherein the second density of the second material is greater than 7.0 g/cc. 
     Clause 17: The putter type golf club head of clause 1, wherein the second density of the second material is at least 2 times greater than the first density of the first material. 
     Clause 18: The putter type golf club head of clause 1, wherein the first material can comprise any one or combination of the following: 8620 alloy steel, S25C steel, carbon steel, maraging steel, 17-4 stainless steel, 303 stainless steel, 304 stainless steel, stainless steel alloy, tungsten, aluminum, aluminum alloy, ADC-12, or any metal suitable for creating a golf club head. 
     Clause 19: The putter golf club head of clause 1, wherein the second material can comprise any one or combination of the following: 8620 alloy steel, S25C steel, carbon steel, maraging steel, 17-4 stainless steel, 303 stainless steel, 304 stainless steel, stainless steel alloy, tungsten, aluminum, aluminum alloy, ADC-12, or any metal suitable for creating a golf club head. 
     Clause 20: The putter golf club head of clause 1, wherein the first material is ADC-12 and the second material is 304 stainless steel.