The Fly-Z XL Combo Set combines two different cavity designs. The long irons incorporate a traditional undercut design for precision and control for the golfer, while the short irons feature a dual cavity hollow design that results in a low, back center of gravity enabling the golfer to hit it higher and farther. The combo set, which includes the dual cavity design hollow and cavity back irons, also include three Fly-Z XL Hybrids that deliver exceptional distance, forgiveness and easy up performance.