These insulatings seals are 3mm thick and this item is for an internal bore of 32mm (i.e. larger bore, normally TT/RN/GP1 carb sizes), to fit flange fitting Amal carbs.(i.e. 2.00" between studs). These thick washers can seal as well as insulating the carb from excess engine heat..
Price per each.
Thicker than the paper type carb gasket we also sell (Item 0452/0453) - and less thick than the Tuffnol spacer rings we also offer, these 3mm thick gaskets/insulating seal's provide a gasket face for Amal flange fitting carbs (with 2.00" between stud centrres - which covers most Amal flange type carbs), but can also offer more heat insulation for the carburettor than the plain paper type washer. These are manufactured by a high quality specialist UK gasket manufacturer .
These are 32mm bore - which is a larger bore size, most suitable for racing carbss. I am supposing this type of gasket/insulating seal is useful if you have an engine running hot, as it keeps the carb cooler (and therefore denser charge)