This type of lock is combined by a 3 digital lock & chain. The chain is protected by vinyl sleeve. The chain locks can be used to lock all brands of bikes (bicycles). Lock the gates of your garden or yards by chain locks to proevent the tools from being stolen. The chain lock can be also used to lock important machinery & equipments for sectury. Chain locks are used only for sectury, please don't use it for lifting or towing. The chains and digital locks can be changed to different kinds in order to meet the requirement of customers.