Amost all the UK chips have migrated from 39mm to 40mm in the past year. Something to do with the automatic machines on the tables. About 1/3 of the London chips are Chipco including Grosvenor and Hard Rock. (Grosvenor own Hard Rock anyway)

I notice the Palms Third Eye Blind chips (Chipco) only fit the 39mm airtite if you force them.

Surely the B&G chips are a mixture of 39 and 40?