GiroDisc Ford S197 Mustang GT500 ('13-14) Rear RotorsThese rotors will only fit 2013 Mustang GT500 with 5. 8L Trinity engine. The Girodisc system is a direct replacement for the OE disc. No modifications are necessary. The disc will bolt directly to the car and work with OE calipers perfectly. By upgrading your brakes with lightweight high performance replacements as opposed to a big brake kit, your factory bias is maintained as well as your ABS efficiency. The Girodisc front rotors are approx 22. 3 lbs