This is the red fibre washer that fits between the main Jet Holder and the float chamber (two being used at this point). The same washer is also used on the main banjo's used from 1940's onwards and fitted to TT's, RN's and GP's as well as Remote float chambers (again 2 fitted per banjo fitting.
We get these washers from a a high quality washer manufacturer specifically for this purpose and are very durable - hence the higher price than those sold in the complete washer sets (Item0164). I always use these washer myself when restoring a carburettor - and they have nice crisp edges that also look correct.
Price is per pair of washers