Barrels, also known as cylinders or cores, are the inner part of a lock which houses the tumblers and receives the key. When the correct key is inserted into the barrel, it aligns the tumblers leaving the barrel free to rotate and open the lock.

Some locks have removable barrels, allowing them to be replaced with a new barrel which can be manufactured to use the same or a different key. A cap and dust cover can also be fitted to help prevent the ingress of dust and dirt.

Barrels in this section are categorised by their diameter.