Golf club heads

Abstract

A golf club head having discreet regions of specific mass relationships, including a lightweight forward portion, to achieve specific mass properties and performance.

1 .- 20 . (canceled) 
     
     
         21 . A golf club head, comprising:
 a face, a sole, a crown, a hosel portion with a hosel bore defining a shaft axis, an adjustable head-shaft connection assembly coupled to the hosel portion and operable to adjust at least one of a loft angle or a lie angle formed when the golf club head is attached to a golf club shaft via the head-shaft connection assembly;   wherein:   the golf club head includes a first material having a first material density of 0.1-3.5 g/cc, a second material having a second material density of 3.6-5.5 g/cc, and a third material having a third material density of 5.6-20.0 g/cc, with the golf club head having a total material volume, a first material volume and a first material mass, a second material volume and a second material mass, and a third material volume and a third material mass;   the golf club head includes a metallic front body portion having a front opening and formed of the second material;   a forward weight is attached to the metallic front body portion;   the golf club head has a head mass of no more than 205 grams, a head volume of at least 410 cc, a center of gravity (CG) having a head origin y-axis (CGy) coordinate of no more than 39 mm and a Zup value of 22-28 mm, a moment of inertia about a club head CG x-axis, Ixx, of no more than 360 kg·mm 2 , and a moment of inertia about a golf club head CG z-axis, Izz, of no more than 530 kg·mm 2 ;   the first material mass is no more than 70% of the head mass;   the second material mass is at least 28% of the head mass;   at least a portion of the crown is formed of non-metallic material;   at least a portion of the face is formed of non-metallic material creating a non-metallic face portion, and the front opening is closed by the non-metallic face portion;   the face has a center face defining an origin for an origin x-axis, an origin y-axis, and an origin z-axis, wherein the origin x-axis is tangential to the face at the origin and parallel to a ground plane, the origin y-axis is perpendicular to the origin x-axis and extends away from the face and is parallel to the ground plane, and the origin z-axis extends vertically from face center and is perpendicular to the ground plane;   a face center vertical plane extends through center face and includes the origin y-axis and the origin z-axis;   a face center horizontal plane extends through a center face and is perpendicular to the face center vertical plane;   a shaft axis vertical plane is parallel to the face center vertical plane and includes the shaft axis;   a 1F vertical plane is parallel to the shaft axis vertical plane and offset 10 mm forward of the shaft axis vertical plane, and a 2F vertical plane is parallel to the shaft axis vertical plane and offset 20 mm forward of the shaft axis vertical plane;   a 1R vertical plane is parallel to the shaft axis vertical plane and offset 10 mm rearward of the shaft axis vertical plane, a 2R vertical plane is parallel to the shaft axis vertical plane and offset 20 mm rearward of the shaft axis vertical plane, a 3R vertical plane is parallel to the shaft axis vertical plane and offset 30 mm rearward of the shaft axis vertical plane, a 4R vertical plane is parallel to the shaft axis vertical plane and offset 40 mm rearward of the shaft axis vertical plane, a 5R vertical plane is parallel to the shaft axis vertical plane and offset 50 mm rearward of the shaft axis vertical plane, a 6R vertical plane is parallel to the shaft axis vertical plane and offset 60 mm rearward of the shaft axis vertical plane, a 7R vertical plane is parallel to the shaft axis vertical plane and offset 70 mm rearward of the shaft axis vertical plane, a 8R vertical plane is parallel to the shaft axis vertical plane and offset 80 mm rearward of the shaft axis vertical plane, and a 9R vertical plane is parallel to the shaft axis vertical plane and offset 90 mm rearward of the shaft axis vertical plane;   a 1T vertical plane is parallel to the face center vertical plane and offset 10 mm toeward of the face center vertical plane, a 2T vertical plane is parallel to the face center vertical plane and offset 20 mm toeward of the face center vertical plane, a 3T vertical plane is parallel to the face center vertical plane and offset 30 mm toeward of the face center vertical plane, a 4T vertical plane is parallel to the face center vertical plane and offset 40 mm toeward of the face center vertical plane, a 5T vertical plane is parallel to the face center vertical plane and offset 50 mm toeward of the face center vertical plane, a 6T vertical plane is parallel to the face center vertical plane and offset 60 mm toeward of the face center vertical plane, a 7T vertical plane is parallel to the face center vertical plane and offset 70 mm toeward of the face center vertical plane, and a 8T vertical plane is parallel to the face center vertical plane and offset 80 mm toeward of the face center vertical plane;   a 1H vertical plane is parallel to the face center vertical plane and offset 10 mm heelward of the face center vertical plane, a 2H vertical plane is parallel to the face center vertical plane and offset 20 mm heelward of the face center vertical plane, a 3H vertical plane is parallel to the face center vertical plane and offset 30 mm heelward of the face center vertical plane, a 4H vertical plane is parallel to the face center vertical plane and offset 40 mm heelward of the face center vertical plane, a 5H vertical plane is parallel to the face center vertical plane and offset 50 mm heelward of the face center vertical plane, a 6H vertical plane is parallel to the face center vertical plane and offset 60 mm heelward of the face center vertical plane, a 7H vertical plane is parallel to the face center vertical plane and offset 70 mm heelward of the face center vertical plane, and a 8H vertical plane is parallel to the face center vertical plane and offset 80 mm heelward of the face center vertical plane;   a 1C horizontal plane is parallel to the face center horizontal plane and offset 10 mm above the face center horizontal plane, a 2C horizontal plane is parallel to the face center horizontal plane and offset 20 mm above the face center horizontal plane, a 3C horizontal plane is parallel to the face center horizontal plane and offset 30 mm above the face center horizontal plane, and a 4C horizontal plane is parallel to the face center horizontal plane and offset 40 mm above the face center horizontal plane;   a 1S horizontal plane is parallel to the face center horizontal plane and offset 10 mm below the face center horizontal plane, and a 2S horizontal plane is parallel to the face center horizontal plane and offset 20 mm below the face center horizontal plane;   the forward weight extends forward of the 2R vertical plane;   a pre-1F mass is a mass of a portion of the golf club head located forward of the 1F vertical plane;   a 4T-4H, 1S-4C, pre-2R mass is a mass of a portion of the golf club head (a) in front of the 2R vertical plane, (b) between the 4T vertical plane and the 4H vertical plane, and (c) between the 1S horizontal plane and the 4C horizontal plane;   a mid-section mass is a mass of a portion of the golf club head between the 8R vertical plane and the 3R vertical plane;   a 3R-2R mass is a mass of a portion of the golf club head between the 3R vertical plane and the 2R vertical plane;   a 4R-3R mass is a mass of a portion of the golf club head between the 4R vertical plane and the 3R vertical plane;   a 5R-4R mass is a mass of a portion of the golf club head between the 5R vertical plane and the 4R vertical plane;   a 6R-5R mass is a mass of a portion of the golf club head between the 6R vertical plane and the 5R vertical plane;   a 7R-6R mass is a mass of a portion of the golf club head between the 7R vertical plane and the 6R vertical plane;   a 8R-7R mass is a mass of a portion of the golf club head between the 8R vertical plane and the 7R vertical plane;   a center-forward-to-mid-section mass ratio is a ratio of the 4T-4H, 1S-4C, pre-2R mass to the mid-section mass, and the center-forward-to-mid-section mass ratio is 0.8-1.3; and   the 6R-5R mass is within 20% of the 5R-4R mass.   
     
     
         22 . The golf club head of  claim 21 , wherein the center-forward-to-mid-section mass ratio is no more than 1.25. 
     
     
         23 . The golf club head of  claim 22 , wherein the 4R-3R mass is within 20% of the 5R-4R mass. 
     
     
         24 . The golf club head of  claim 23 , wherein the total material volume is at least 70 cc, the portion of the golf club head between the 4R vertical plane and the 3R vertical plane has a maximum 4R-3R section width, the portion of the golf club head between the 8R vertical plane and the 7R vertical plane has a minimum 8R-7R section width, and the maximum 4R-3R section width is at least 20% greater than the minimum 8R-7R section width. 
     
     
         25 . The golf club head of  claim 24 , wherein the first material volume is 69-79% of the total material volume. 
     
     
         26 . The golf club head of  claim 25 , wherein the ratio of the 3R-2R mass to the 4R-3R mass is at least 1.1, and the total material volume is 71.2-85.2 cc. 
     
     
         27 . The golf club head of  claim 25 , wherein the first material volume is 50-77.8 cc. 
     
     
         28 . The golf club head of  claim 27 , wherein the first material volume is no more than 64.6 cc. 
     
     
         29 . The golf club head of  claim 25 , wherein the second material volume is 12-32% of the total material volume. 
     
     
         30 . The golf club head of  claim 29 , wherein the second material mass is 66-82 grams. 
     
     
         31 . The golf club head of  claim 24 , wherein the portion of the golf club head between the 4R vertical plane and the 3R vertical plane has a maximum 4R-3R section height, the portion of the golf club head between the 8R vertical plane and the 7R vertical plane has a minimum 8R-7R section height, and the maximum 4R-3R section height is at least 20% greater than the minimum 8R-7R section height. 
     
     
         32 . The golf club head of  claim 24 , wherein the mid-section mass is no more than 50% of a pre-SAVP mass, where the pre-SAVP mass is a mass of a portion of the golf club head located forward of the shaft axis vertical plane. 
     
     
         33 . The golf club head of  claim 24 , wherein the 4T-4H, 1S-4C, pre-2R mass is less than 36 grams, and the mid-section mass is less than 36 grams. 
     
     
         34 . The golf club head of  claim 24 , further including a rear weight having a density of at least 7 g/cc and extending behind the 9R vertical plane. 
     
     
         35 . The golf club head of  claim 34 , wherein the forward weight further comprises two forward weights attached to the metallic front body portion. 
     
     
         36 . The golf club head of  claim 34 , further including an aluminum rear ring portion having a density of less than 3 g/cc and attached to the metallic front body portion and forming a crown opening and a sole opening, wherein a lightweight composite crown covers the crown opening and has a crown mass of less than 20 grams, and a lightweight composite sole plate covers the sole opening and has a sole plate mass of less than 30 grams. 
     
     
         37 . The golf club head of  claim 36 , wherein the rear weight contacts the aluminum rear ring portion. 
     
     
         38 . The golf club head of  claim 36 , wherein the aluminum rear ring portion is attached to the metallic front body portion at a toe ring joint and a heel ring joint, the toe ring joint is located a toe joint distance from the shaft axis vertical plane, the heel ring joint is located a heel joint distance from the shaft axis vertical plane, and the toe joint distance is not equal to the heel joint distance. 
     
     
         39 . The golf club head of  claim 38 , wherein the toe joint distance is 105-200% of the heel joint distance. 
     
     
         40 . The golf club head of  claim 38 , wherein a lowest portion of the heel joint is located at a heel joint elevation, a lowest portion of the toe joint is located at a toe joint elevation, and the toe joint elevation is at least 130% of the heel joint elevation. 
     
     
         41 . The golf club head of  claim 38 , wherein a portion of the aluminum rear ring portion is located above an elevation of the center face, and a portion of the aluminum rear ring portion is located below the elevation of the center face. 
     
     
         42 . The golf club head of  claim 24 , wherein the pre-1F mass is at least 4 grams and less than 22.5 grams, a pre-SAVP central-4 array mass is less than 4 grams, where the pre-SAVP central-4 array mass is a mass of a portion of the golf club head located (a) in front of the shaft axis vertical plane, (b) between the 1T vertical plane and the 1H vertical plane, and (c) between the 1S horizontal plane and the 1C horizontal plane. 
     
     
         43 . The golf club head of  claim 24 , wherein the pre-1F mass is at least 7 grams and less than 20 grams. 
     
     
         44 . The golf club head of  claim 24 , wherein a ratio of the 3R-2R mass to the 4R-3R mass is no more than 1.55. 
     
     
         45 . The golf club head of  claim 24 , wherein a pre-SAVP mass is a mass of a portion of the golf club head located forward of the shaft axis vertical plane, and the pre-SAVP mass is less than 69 grams. 
     
     
         46 . The golf club head of  claim 24 , further including a rear ring portion having a density of less than 3 g/cc and attached to the metallic front body portion and forming a crown opening, wherein a lightweight composite crown covers the crown opening and has a crown mass of less than 20 grams. 
     
     
         47 . A golf club head, comprising:
 a face, a sole, a crown, a hosel portion with a hosel bore defining a shaft axis, an adjustable head-shaft connection assembly coupled to the hosel portion and operable to adjust at least one of a loft angle or a lie angle formed when the golf club head is attached to a golf club shaft via the head-shaft connection assembly;   wherein:   the golf club head includes a first material having a first material density of 0.1-3.5 g/cc, a second material having a second material density of 3.6-5.5 g/cc, and a third material having a third material density of 5.6-20.0 g/cc, with the golf club head having a total material volume of at least 70 cc, a first material volume of 69-79% of the total material volume, a first material mass, a second material volume, a second material mass, a third material volume, and a third material mass;   the golf club head includes a metallic front body portion having a front opening and formed of the second material;   a forward weight is attached to the metallic front body portion;   the golf club head has a head mass of no more than 208 grams, a head volume of at least 410 cc, a Zup value of 22-28 mm;   the first material mass is no more than 70% of the head mass;   the second material mass is at least 28% of the head mass;   at least a portion of the crown is formed of non-metallic material;   at least a portion of the face is formed of non-metallic material creating a non-metallic face portion, and the front opening is closed by the non-metallic face portion;   the face has a center face defining an origin for an origin x-axis, an origin y-axis, and an origin z-axis, wherein the origin x-axis is tangential to the face at the origin and parallel to a ground plane, the origin y-axis is perpendicular to the origin x-axis and extends away from the face and is parallel to the ground plane, and the origin z-axis extends vertically from face center and is perpendicular to the ground plane;   a face center vertical plane extends through center face and includes the origin y-axis and the origin z-axis;   a face center horizontal plane extends through a center face and is perpendicular to the face center vertical plane;   a shaft axis vertical plane is parallel to the face center vertical plane and includes the shaft axis;   a 1F vertical plane is parallel to the shaft axis vertical plane and offset 10 mm forward of the shaft axis vertical plane, and a 2F vertical plane is parallel to the shaft axis vertical plane and offset 20 mm forward of the shaft axis vertical plane;   a 1R vertical plane is parallel to the shaft axis vertical plane and offset 10 mm rearward of the shaft axis vertical plane, a 2R vertical plane is parallel to the shaft axis vertical plane and offset 20 mm rearward of the shaft axis vertical plane, a 3R vertical plane is parallel to the shaft axis vertical plane and offset 30 mm rearward of the shaft axis vertical plane, a 4R vertical plane is parallel to the shaft axis vertical plane and offset 40 mm rearward of the shaft axis vertical plane, a 5R vertical plane is parallel to the shaft axis vertical plane and offset 50 mm rearward of the shaft axis vertical plane, a 6R vertical plane is parallel to the shaft axis vertical plane and offset 60 mm rearward of the shaft axis vertical plane, a 7R vertical plane is parallel to the shaft axis vertical plane and offset 70 mm rearward of the shaft axis vertical plane, a 8R vertical plane is parallel to the shaft axis vertical plane and offset 80 mm rearward of the shaft axis vertical plane, and a 9R vertical plane is parallel to the shaft axis vertical plane and offset 90 mm rearward of the shaft axis vertical plane;   a 1T vertical plane is parallel to the face center vertical plane and offset 10 mm toeward of the face center vertical plane, a 2T vertical plane is parallel to the face center vertical plane and offset 20 mm toeward of the face center vertical plane, a 3T vertical plane is parallel to the face center vertical plane and offset 30 mm toeward of the face center vertical plane, a 4T vertical plane is parallel to the face center vertical plane and offset 40 mm toeward of the face center vertical plane, a 5T vertical plane is parallel to the face center vertical plane and offset 50 mm toeward of the face center vertical plane, a 6T vertical plane is parallel to the face center vertical plane and offset 60 mm toeward of the face center vertical plane, a 7T vertical plane is parallel to the face center vertical plane and offset 70 mm toeward of the face center vertical plane, and a 8T vertical plane is parallel to the face center vertical plane and offset 80 mm toeward of the face center vertical plane;   a 1H vertical plane is parallel to the face center vertical plane and offset 10 mm heelward of the face center vertical plane, a 2H vertical plane is parallel to the face center vertical plane and offset 20 mm heelward of the face center vertical plane, a 3H vertical plane is parallel to the face center vertical plane and offset 30 mm heelward of the face center vertical plane, a 4H vertical plane is parallel to the face center vertical plane and offset 40 mm heelward of the face center vertical plane, a 5H vertical plane is parallel to the face center vertical plane and offset 50 mm heelward of the face center vertical plane, a 6H vertical plane is parallel to the face center vertical plane and offset 60 mm heelward of the face center vertical plane, a 7H vertical plane is parallel to the face center vertical plane and offset 70 mm heelward of the face center vertical plane, and a 8H vertical plane is parallel to the face center vertical plane and offset 80 mm heelward of the face center vertical plane;   a 1C horizontal plane is parallel to the face center horizontal plane and offset 10 mm above the face center horizontal plane, a 2C horizontal plane is parallel to the face center horizontal plane and offset 20 mm above the face center horizontal plane, a 3C horizontal plane is parallel to the face center horizontal plane and offset 30 mm above the face center horizontal plane, and a 4C horizontal plane is parallel to the face center horizontal plane and offset 40 mm above the face center horizontal plane;   a 1S horizontal plane is parallel to the face center horizontal plane and offset 10 mm below the face center horizontal plane, and a 2S horizontal plane is parallel to the face center horizontal plane and offset 20 mm below the face center horizontal plane;   the forward weight extends forward of the 2R vertical plane;   a pre-1F mass is a mass of a portion of the golf club head located forward of the 1F vertical plane;   a 4T-4H, 1S-4C, pre-2R mass is a mass of a portion of the golf club head (a) in front of the 2R vertical plane, (b) between the 4T vertical plane and the 4H vertical plane, and (c) between the 1S horizontal plane and the 4C horizontal plane;   a mid-section mass is a mass of a portion of the golf club head between the 8R vertical plane and the 3R vertical plane;   a 3R-2R mass is a mass of a portion of the golf club head between the 3R vertical plane and the 2R vertical plane;   a 4R-3R mass is a mass of a portion of the golf club head between the 4R vertical plane and the 3R vertical plane;   a 7R-6R mass is a mass of a portion of the golf club head between the 7R vertical plane and the 6R vertical plane;   a 8R-7R mass is a mass of a portion of the golf club head between the 8R vertical plane and the 7R vertical plane;   a forward heel and toe mass is a sum of:
 a mass of a portion of the golf club head (a) in front of the 2R vertical plane, (b) between the 4H vertical plane and the 8H vertical plane, and (c) between the 1S horizontal plane and the 4C horizontal plane; and 
 a mass of a portion of the golf club head (a) in front of the 2R vertical plane, (b) between the 4T vertical plane and the 8T vertical plane, and (c) between the 1S horizontal plane and the 4C horizontal plane; 
   a center-forward-to-mid-section mass ratio is a ratio of the 4T-4H, 1S-4C, pre-2R mass to the mid-section mass, and the center-forward-to-mid-section mass ratio is 0.8-1.3; and   a center-forward-to-HT mass ratio is a ratio of the a 4T-4H, 1S-4C, pre-2R mass to the forward heel and toe mass, and the center-forward-to-HT mass ratio is 0.8-1.3.   
     
     
         48 . A golf club head, comprising:
 a face, a sole, a crown, a hosel portion with a hosel bore defining a shaft axis, an adjustable head-shaft connection assembly coupled to the hosel portion and operable to adjust at least one of a loft angle or a lie angle formed when the golf club head is attached to a golf club shaft via the head-shaft connection assembly;   wherein:   the golf club head includes a first material having a first material density of 0.1-3.5 g/cc, a second material having a second material density of 3.6-5.5 g/cc, and a third material having a third material density of 5.6-20.0 g/cc, with the golf club head having a total material volume, a first material volume, a first material mass, a second material volume of 12-32% of the total material volume, a second material mass, a third material volume, and a third material mass;   the golf club head includes a metallic front body portion having a front opening and formed of the second material;   the golf club head has a head mass of no more than 209 grams and a head volume of at least 410 cc;   the first material mass is no more than 70% of the head mass;   the second material mass is at least 28% of the head mass;   at least a portion of the crown is formed of non-metallic material;   at least a portion of the face is formed of non-metallic material creating a non-metallic face portion, and the front opening is closed by the non-metallic face portion;   the face has a center face defining an origin for an origin x-axis, an origin y-axis, and an origin z-axis, wherein the origin x-axis is tangential to the face at the origin and parallel to a ground plane, the origin y-axis is perpendicular to the origin x-axis and extends away from the face and is parallel to the ground plane, and the origin z-axis extends vertically from face center and is perpendicular to the ground plane;   a face center vertical plane extends through center face and includes the origin y-axis and the origin z-axis;   a face center horizontal plane extends through a center face and is perpendicular to the face center vertical plane;   a shaft axis vertical plane is parallel to the face center vertical plane and includes the shaft axis;   a 1F vertical plane is parallel to the shaft axis vertical plane and offset 10 mm forward of the shaft axis vertical plane, and a 2F vertical plane is parallel to the shaft axis vertical plane and offset 20 mm forward of the shaft axis vertical plane;   a 1R vertical plane is parallel to the shaft axis vertical plane and offset 10 mm rearward of the shaft axis vertical plane, a 2R vertical plane is parallel to the shaft axis vertical plane and offset 20 mm rearward of the shaft axis vertical plane, a 3R vertical plane is parallel to the shaft axis vertical plane and offset 30 mm rearward of the shaft axis vertical plane, a 4R vertical plane is parallel to the shaft axis vertical plane and offset 40 mm rearward of the shaft axis vertical plane, a 5R vertical plane is parallel to the shaft axis vertical plane and offset 50 mm rearward of the shaft axis vertical plane, a 6R vertical plane is parallel to the shaft axis vertical plane and offset 60 mm rearward of the shaft axis vertical plane, a 7R vertical plane is parallel to the shaft axis vertical plane and offset 70 mm rearward of the shaft axis vertical plane, a 8R vertical plane is parallel to the shaft axis vertical plane and offset 80 mm rearward of the shaft axis vertical plane, and a 9R vertical plane is parallel to the shaft axis vertical plane and offset 90 mm rearward of the shaft axis vertical plane;   a 1T vertical plane is parallel to the face center vertical plane and offset 10 mm toeward of the face center vertical plane, a 2T vertical plane is parallel to the face center vertical plane and offset 20 mm toeward of the face center vertical plane, a 3T vertical plane is parallel to the face center vertical plane and offset 30 mm toeward of the face center vertical plane, a 4T vertical plane is parallel to the face center vertical plane and offset 40 mm toeward of the face center vertical plane, a 5T vertical plane is parallel to the face center vertical plane and offset 50 mm toeward of the face center vertical plane, a 6T vertical plane is parallel to the face center vertical plane and offset 60 mm toeward of the face center vertical plane, a 7T vertical plane is parallel to the face center vertical plane and offset 70 mm toeward of the face center vertical plane, and a 8T vertical plane is parallel to the face center vertical plane and offset 80 mm toeward of the face center vertical plane;   a 1H vertical plane is parallel to the face center vertical plane and offset 10 mm heelward of the face center vertical plane, a 2H vertical plane is parallel to the face center vertical plane and offset 20 mm heelward of the face center vertical plane, a 3H vertical plane is parallel to the face center vertical plane and offset 30 mm heelward of the face center vertical plane, a 4H vertical plane is parallel to the face center vertical plane and offset 40 mm heelward of the face center vertical plane, a 5H vertical plane is parallel to the face center vertical plane and offset 50 mm heelward of the face center vertical plane, a 6H vertical plane is parallel to the face center vertical plane and offset 60 mm heelward of the face center vertical plane, a 7H vertical plane is parallel to the face center vertical plane and offset 70 mm heelward of the face center vertical plane, and a 8H vertical plane is parallel to the face center vertical plane and offset 80 mm heelward of the face center vertical plane;   a 1C horizontal plane is parallel to the face center horizontal plane and offset 10 mm above the face center horizontal plane, a 2C horizontal plane is parallel to the face center horizontal plane and offset 20 mm above the face center horizontal plane, a 3C horizontal plane is parallel to the face center horizontal plane and offset 30 mm above the face center horizontal plane, and a 4C horizontal plane is parallel to the face center horizontal plane and offset 40 mm above the face center horizontal plane;   a 1S horizontal plane is parallel to the face center horizontal plane and offset 10 mm below the face center horizontal plane, and a 2S horizontal plane is parallel to the face center horizontal plane and offset 20 mm below the face center horizontal plane;   a pre-1F mass is a mass of a portion of the golf club head located forward of the 1F vertical plane;   a 4T-4H, 1S-4C, pre-2R mass is a mass of a portion of the golf club head (a) in front of the 2R vertical plane, (b) between the 4T vertical plane and the 4H vertical plane, and (c) between the 1S horizontal plane and the 4C horizontal plane;   a mid-section mass is a mass of a portion of the golf club head between the 8R vertical plane and the 3R vertical plane;   a 3R-2R mass is a mass of a portion of the golf club head between the 3R vertical plane and the 2R vertical plane;   a 4R-3R mass is a mass of a portion of the golf club head between the 4R vertical plane and the 3R vertical plane;   a 7R-6R mass is a mass of a portion of the golf club head between the 7R vertical plane and the 6R vertical plane;   a 8R-7R mass is a mass of a portion of the golf club head between the 8R vertical plane and the 7R vertical plane;   a forward heel and toe mass is a sum of:
 a mass of a portion of the golf club head (a) in front of the 2R vertical plane, (b) between the 4H vertical plane and the 8H vertical plane, and (c) between the 1S horizontal plane and the 4C horizontal plane; and 
 a mass of a portion of the golf club head (a) in front of the 2R vertical plane, (b) between the 4T vertical plane and the 8T vertical plane, and (c) between the 1S horizontal plane and the 4C horizontal plane; 
   a center-forward-to-mid-section mass ratio is a ratio of the 4T-4H, 1S-4C, pre-2R mass to the mid-section mass, and the center-forward-to-mid-section mass ratio is 0.8-1.3; and   a forward-HT-to-mid-section mass ratio is a ratio of the forward heel and toe mass to the mid-section mass, and the forward-HT-to-mid-section mass ratio is 0.8-1.3.