B22 bayonet cap base
B22 is the standard bayonet cap base used in the UK and Commonwealth countries — it pushes in and twists to lock rather than using a screw thread.
Exact specs
| Designation | B22 (BC, Bayonet Cap) |
|---|---|
| Base diameter | 22 mm |
| Mounting method | Push and twist (bayonet lugs) |
| Primary region | UK, Ireland, Australia, India, and Commonwealth countries |
| Typical wattage range | 5W–100W (LED/halogen equivalent) |
What fixtures commonly use it
Standard ceiling pendants, table lamps, and floor lamps in the UK, Australia, and South Africa commonly use B22 bayonet sockets.
What it's interchangeable with
B22d (double-contact bayonet) is the standard form. LED B22 bulbs replace B22 halogen and incandescent bulbs directly.
What it's NOT interchangeable with
B22 bayonet sockets do not accept Edison screw bulbs (E27, E26) — the twist-lock vs screw mechanisms are fundamentally different and sizes do not align.
Common mistakes
- Trying to screw an E27 into a B22 socket when traveling or moving between countries.
- Buying the wrong base when shopping online without checking fixture type.