US Patent 7901298 Golf club head with improved mass distribution

A golf club head having a striking wall, a front surface, a sole portion extending rearwardly from the rear surface, the sole portion having a forward end, a rearward end, an upper surface and a lower surface. The intersection of the upper surface and the rear surface defines an interior sole line. The intersection of the upper surface and the rearward end defines a trailing edge exterior sole line. The upper surface comprises a sink portion having substantial variation in heel-to-toe contour.