Cambox Bearing - Camshaft Back Roller Bearing : as fitted to the Model 30M/40M (Manx) cambox backplate - identifiable from the standard International type, in that the Manx backplate is in magnesium. These are the correct RHP C3 bearings - now very rare and hard to get hold of. (C3 type are slightly looser tolerance bearings and were originally used in these racing engines. The C3 type are not essential for cambox's - but are definitely a rare luxury today, when even the standard RHP type have been unavailable for the last couple of years). Not cheap - but the proper thing and when they are gone they are gone!!