The invention includes a golf club iron head, correlated sets of individually numbered golf club irons, methods of matching a golf club to a golfer, and methods of matching a set of golf clubs to a golfer. In one implementation, a golf club iron head includes a front striking face, a sole, a toe, and a heel. The front striking face has a series of grooves of a common cross sectional shape from the top to the bottom. Individual grooves have a base and opposing sidewalls which diverge from the base and extend outwardly in the direction of the front striking face. The sidewalls include opposing protrusions extending into the groove proximate the front striking face. In one implementation, the front striking face of a golf club iron head defines a symmetrical groove cross section. The groove base comprises a protrusion extending in the direction of the front striking face. The base protrusion has an apex received inwardly of the front striking face. In one implementation, a correlated set of individually numbered golf club irons have heads progressing from a high numbered head to a low numbered head. For at least two chosen pairs of heads within the set, the grooves in the heads are configured to provide decreasing golf ball spin in going from the lower numbered head to the higher numbered head in the pair if the golf ball were hit by the faces by identical impacts at the same loft angle.