Girodisc Ford S550 Mustang Rear RotorsThese GiroDisc 2 piece rotors are a direct replacement for the rear rotors on the S550 Mustang. Our 2 piece, fully floating assemblies help shed unsprung weight and rotating mass from the front axle of the vehicle. The rotor rings are machined from a proprietary casting made of high carbon steel formulated to GiroDisc's specifications. This superior metallurgy results in a rotor that holds up better, and the 48 curved vanes act as a centrifugal pump