BC Copper Switched Lampholder With 10mm Entry 
This Lamp holder has a 10mm thread in the base for fixing it to any 10mm fixing.
Comes with a shade ring to attach a 30mm lamp shade.
There is an earth connection inside the lamp holder.
Lamp holder Cap: BC | B22 | Bayonet Cap
Diameter including shade ring: 32mm
Fixing Thread Size: 10mm