This lampholder is a standard B22 lampholder except it has a lock collar at the bottom with an internal locking screw.
This prevents any unwanted untwisting of the lampholder.
Lamp Cap: BC | B22 | Bayonet Cap
Min Shade Hole Size: 26mm
Max Shade Hole Size: 32mm
Max Wattage: 60w
Finish: Antique Brass