Bayonet Cap Lampholders for the b22 lamps. The BC Lampholder is one of the most popular in the UK and you can have Switched BC Lampholders as well as Un-Switched BC Lampholders. The lampholders have a thread in the cap or base which can be used to mount to a male thread. There is 10mm and 1/2″ variations with the 10mm having the largest range. They come with or with-out a switch and there are batten versions as well. White Plastic BC Lampholders are the lowest in price but are used on a lot of off the shelf lamps.