Performance Machine Front Radial Mount Caliper Bracket For Harley The Radial Mount design anchors the caliper next to the rotor's entrance point and exit point yielding a caliper that is stiffer than traditional calipers and holds a more precise caliper to rotor alignment. Features: CNC machined from billet aluminum Mounting hardware sold separately Works with Performance Machine radial mount caliper or any radial mount caliper with a 4.25 mounting bolt spread.