These single use numbered plastic chastity locks are ideal for keeping tabs on a naughty plaything. Each lock is designed to be tamper evident. Any attempt to remove the lock will destroy it beyond repair. Just insert the end of the lock into the slot. It works like a zip tie resisting any attempt to loosen or remove it. Each one has a unique number on it so even if the lock is replaced the number will reveal that it has been changed. The plastic material is ideal for polycarbonate or plastic cages which will not set off metal detectors and are lightweight and water safe. Numbered locks are also great for adding an extra element of control as well as temptation since unlike metal locks which are unable to be opened without the key the plastic locks can be removed if the need arises. Your plaything will have to restrain themselves from removing the lock since all you have to do is compare the serial number with the one they started with to see if you have some disciplining to do...