bayonet cap

In Britain and countries with a historical connection to Britain, the bayonet cap (BC) is the usual mount.

BA15, a 15 mm base, can also be referred to as SBC standing for small bayonet cap.

The number refers to the diameter of the base (e.g., BA22 is a 22 mm diameter bayonet cap lamp).

Various styles of bayonet cap and mounts are used for a variety of sizes and types of bulbs, including spots and halogens.

It is accessed by using a coin slot type threaded cap and is superior in design to that of the bayonet caps that surfaced as of the M6.