Two sides braking force Ball bearing actuation system Two sides adjusted the pad gap Caliper: Two sides braking force Ball bearing actuation system Rotor: Diameter: 160MM Material : Stainsless steel Front brake (F160-R140)= If you install this brake on front wheel, it suit for 160mm disc rotor, if you install this brake on your rear wheel, it suit for 140mm disc rotor. Rear brake (F180-R160)=If you install this brake on Front wheel, it suit for 180mm disc rotor. If you install this brake on Rear wheel, it suit for 160mm disc rotor. Also avaiLable:140MM/160MM/180MM/203MM Weight : 228g/pcs Package: 1pc front brake / Rear Brake or 1 Set Front and Rear brakes Note:Normally, it should not to use the brake without brake rotors. the right way which use the brake is it must install the brake rotors, and then it can use normally.