Features: Suitable for important places, such as office, house, warehouse and others. Against versatile key: The internal construction of the lock has been inovated and modified from the usual ball to the special multi layered one. In effect, versatile key cannot open the lock in any way. Against sawing: Hardened steel shackle cannot be cut by a saw. Cannot be prized: The device is made of very hard Ar steel ball to pin the shackle. It is very strong therefore it cannot be prized by force. Against drill: Hardened lock shaft cover cannot be drilled.