US Patent 7594864 Golf club head with improved mass distribution

A golf club having a sole portion extending rearwardly from a rear surface of the head, wherein the sole portion includes 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 lone. 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, including variation of at least one of: the height of the trailing edge or exterior sole line relative to the height of the interior sole line, measured in vertical alignment; the height of any of the interior sole line or trailing edge or exterior sole line relative to the height of the general outer periphery measured in vertical alignment; and concavity as defined by forward-to-rear contour.