ProMatrix Front and Rear Rotor Kits offer measurable brake performance improvements to racers and enthusiasts using the OE factory brake calipers. Two piece aluminum hat and GT 72 32 Curved Vane Spec - 37 assemblies are used to provide high temperature durability for the track and high - tech style for the street. 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.