Single piston aluminum caliper, patented bimetal aluminum/stainless piston, oil impregnated bronze bushings, ceramic pads with stainless steel backing plates stainless steel slider pins, GalvX coated hub and galvanized mounting bracket. Precision bearings, seals, and grease factory installed. Factory pre-installed stainless steel slider pins. Each kit is for one wheel, includes mounting bracket. Stainless Steel rotor with venting holes for faster cooling. G4.5 Upgrade Kits replaces G4 caliper with G5 caliper with lifetime pads 5 on 4-1/2" bolt pattern.