Valve spring heat insulating washer for all Norton twins and matchless twins 1964+ (each). 4 required per engine with normal cams; only two on the exhaust with a 2S cam and none with a 4S cam BUT check your head first before excluding them.Originally fitted in 1953, if only two are fitted they go under the exhaust-valve cups. Original part numbers: H12/16339; 16339; 067845; 06-7845 - valve spring heat resisting washer
