Brand: ZoomTwo sides braking forceBall bearing actuation systemTwo sides adjusted the pad gapCaliper: Two sides braking forceBall bearing actuation systemBrake Pads: IncludedBoth 51mm IS&74mm Post mountingRotor: Diameter: 160MMMaterial : SUS410 Stainsless steelFront 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.It is also suit for Kugoo g-booster scooter, when you install it on the left side of rear wheel.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 Suit for:140MM/160MM/180MM/203MMWeight : 228g/pcSuit for: A or B pilarPackage: 1pc front brake / Rear Brake or 1 Set Front and Rear brakesNote: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.