US Patent 6991558 Golf club head

A club head for a golf club comprises a strike face and an outer shell. The strike face and the outer shell define a head volume of the club head. The club head has a first axis that extends generally horizontally and parallel to the strike face, a first moment of inertia about the first axis, a second axis that lies generally vertically and perpendicular to the first horizontal axis, a second moment of inertia about the second axis, and a center of gravity lying below a horizontal centerline of the club head. The first moment of inertia in units of kg-mm2 is greater than or equal to approximately 77 plus 0.46 times the head volume in units of cm3.