Kryptonite Gravity WheelBoltz Gravity Line WheelBoltz harnesses the power of gravity to prevent the removal of wheels When the bike is upright, the WheelBoltz are locked and can only be unlocked with the bike turned upside down EASY TO INSTALL. No special keys required. (5mm hex wrench included) Industry standard axle fitment lengths of 130mm (front) / 150mm (back) LIGHTWEIGHT- only 120gms per set Product weight: .17 lbs (.77kgs)