Abstract: Golf club heads each having a specifically contoured back side shaped to provide an optimal three-dimensional mass distribution, the invention preferably takes the form of "oversize" iron club heads having an unusually large "sweet spot" while retaining traditional iron head weights. The optimally distributed mass of each head is provided over the entire back side of the head with the back side contour interacting with face-stiffening ribs located on the top and toe of the head to yield performance advantages. The versatility found in the contouring of the back side of each head to yield optimal mass distribution allows the hitting area of each club face in a set of clubs to increase incrementally as the loft of each iron decreases, thereby resulting in a more uniform "sight picture" between clubs as viewed by the player.