Wilwood 160 8953 Rotor SV GT 60 Iron RH THMotorsports Wilwood Disc Brakes GT 72 Straight Vane Rotor Wilwood Rotor GT48 SPC 37 LH Bedded 12.90 x 1.38 12 on 7.15in eBay Wilwood Rotor SV GT 72 SPC 37 RH BLK 14.25 x 1.25 12 on 9.19in Wilwood Disc Brakes Hat (Bell) Mount Rotors. Wilwood's GT 72 Curved Vane Spec 37 rotors are manufactured from a proprietary iron alloy developed to withstand extreme temperatures with the highest possible degree of resistance against distortion, warping, cracking, and wear. The formulation for this alloy is a derivative of technology and materials that were significant in the development of the extreme duty military spec rotors that are manufactured by Wilwood. Every Spec 37 rotor is precision machined to less than . 001" run out, flatness, and parallelism. Combined with our proven GT Series asymmetrical face slot pattern and individual dynamic balancing, you are assured the smoothest braking available.