THESE FIT MOST MODERN BRASS LAMP HOLDERS, HOWEVER, I CANNOT FULLY GUARANTEE THESE WILL FIT YOUR LAMP HOLDER Read below please.
Photos of what they DO fit shown.You are responsible to ensure they will fit-all spares are non-returnable.
THEY DO NOT FIT LAURA ASHLEY LAMP HOLDERS OF THE TYPE SHOWN IN FINAL IMAGE, this is a one off design and is 2mm smaller.
Pair (2) of British(Birmingham) made solid raw brass lamp holder retaining rings for most brass UK lamp holders after 1970.*
Overall diameter is 31.6mm, Thread is 28mm-(Visible hole measures at 25.8mm aperture) and approximately 3.5mm thick with machined knurled edges. The thread pitch is approximately 26TPI or 1mm.
*Some much older (and foreign-made) lamp holders are slightly wider and quite often have a coarser thread.
These fit Lilley, Jeani and Lyvia brands in my own selection  of modern lamp holders.
Most plastic holders have a slightly coarser thread pitch and E14 and E27 have 1,5mm pitch thread-visibly much wider. THEY WILL DEFINITELY NOT FIT PLASTIC LAMP HOLDERS.
ROYAL MAIL POSTAL-PRICE INCREASES
Please note that as of 2nd October 2023 Royal Mail now charge £1.55 for a large letter up to 100g only, the packing materials cost 15p average and eBay take 12.8% of any postage charged. (25p of £1.95)It is regrettable that it now COSTS SELLERS £1.95 to send a tiny large letter. Over 100g now costs over £3.00 - same as a parcel.
NO PROFIT IS MADE ON POSTAGE AT ALL - NOT ONE PENNY.