Old English Cord Grip with Male 10mm Thread 
This Old English Cord grip is perfect for converting a lampholder with a 10mm hole into a pendant lampholder.
Meaning you can suspend the lampholder from a cable.
This Old English Cord Grip with Male 10mm Thread will simply screw into the back of the 10mm lampholder.
Height (ex thread): 20mm Apprx
Thread Diameter: 10mm
Thread Pitch: 1mm