US Patent 8167737 Wood-type golf club head

A hollow wood-type golf club head with stable flight direction and flight distance performances, the club head having a moment of inertia Ix 4,000 to 5,900 g·cm2 about a vertical axis passing through the club head's center of gravity, and comprising a face with face bulge and face roll such that the radius of curvature Rx of the face bulge is from 12 to 25 inches, and the Ry/Rx ratio of the radius of curvature Ry of the face roll to the radius of curvature Rx of the face bulge is 0.50 to 0.90.