Not sure what the size is tbh, I'll wait until it arrives & measure it. I've bought far too many mounts without measuringIncluding a one piece that's too long for the compact scopes I've got & mounts too short for the dia of another scope.
I've had two Mercuries in the past & never realised until recently that BSA have their own odd rail size.
Had a horribly hectic day today in baking heat, every time I look up there is a calendar right in front of me, and I'm thinking "two weeks today & I'll be there, away from all this".![]()