GP 310 4 Piston Motorcycle Rear Brake Caliper, 1984-up Harley Davidson, 1.25″ / 1.25″ Piston Bores, 11.5″ Rotor Dia., 0.25″ Disc Width, Right Hand, Standard 3.50″ Mount Spacing, Black Powder Coat Finish|Wilwood GP 310 4 Piston Motorcycle Rear Brake Caliper 1984-up Harley Davidson.