Legal CB.

Approved CB transceivers: FM only, UK or CEPT frequencies only. These usually have a stamp mark to show approval.
Dipole antennas: No more than 1/2 wave (around 18 foot) in length, no more than 55mm diameter.
Monopole antennas: No more than 5/8 wave (around 21 foot) in length, no more than 55mm diameter.
Microphones: Any type is allowed, although incorrect setting of an amplified type may take the transceiver beyond legal specification.
SWR meter: Any type, but it may only be connected while testing or adjusting the antenna.
Accessories: An accessory which does not make the CB operate outside of the legal limits and does not form any product specifically listed as illegal.
Add-on circuits: Any add-on that does not make the CB operate outside of the legal limits, and does not form any product specifically listed as illegal.