Old English Reducing Bush 1/2" to 10mm 
This Old English Reducing bush 1/2" to 10mm is perfect for reducing the 1/2" thread on your light fitting to a standard 10mm entry lampholder.
As 10mm is the more popular version of the 2 types of threads this is perfect product to use.
The Old English reducing bush 1/2" to 10mm has a female 1/2" thread and a male 10mm thread.
Female thread: 1/2"
Male thread: 10mm
Plating Finish: Old English