Kryptonite keeper 785 integrated chain as a leader in action sports security and the creator of the original bicycle u lock in the bicycle security category in 1971 kryptonite offers premium quality security products features 7mm four sided chain links made from 3t manganese steel patent pending end link design secures chain to hardened deadbolt eliminating critical vulnerability hardened deadbolt design provides extra holding power high security disc style cylinder is pick and drill resistant