Polished billet-aluminum hubs come standard with screw-on dust covers and feature both 4-1/2" and 4-3/4" bolt circles. The vented rotors are 11.75" in diameter and .810" thick; 2-1/2"-long studs are included (3" studs are optional). All necessary bearings, seals and hardware needed for installation are supplied. Rotors feature curved gas-relief slots to aid in braking. You have a choice of two popular, four-piston Wilwood calipers, these assemblies will fit most 15"-diameter wheels. Choose from black matte or polished finish.