TaylorMade Tour Preferred MC Iron Set, RH 4-PW, Stiff Irons contain a shallow muscle cavity to increase Moment of Inertia, while preserving the workability, feel and stability of a Tour inspired iron. The MC models sport a slightly larger topline, length and sole-width than their true muscleback counterparts but can still provide the playability needed in order to be used by PGA Tour professionals like Sergio Garcia and Justin Rose.