What does 10mm or 1/2" entry mean?

There are 2 more common thread sizes in the world of lighting, 10mm and 1/2" (12.7mm) approx. To find out what one you need is simple, there should be a thread that's sticking out of your lamp fitting were the lampholders screws onto, you simply need to measure the outside diameter of that thread. 

Most lampholders are 10mm now days but 1/2" is still widely used.

10mm will measure around 9.5mm and the 1/2" will be around 12mm

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  • You make no mention of a 7mm threaded holder entry. I am searching for one so far without success





  • Hi Harry,

    I know of an 8mm thread which are rare but never heard of a 7mm.


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