Twin row caged ball bearing. Fitted to Model 30M/40M (Manx) SOHC engines. This bearing as it was originally manufactured (with bronze cage) is now obsolete and unobtainable in original '3 spot' specification. The C3\3-spot version is really an essential specification, as this means a looser tolerence than normal bearings - very important on Norton engines to ensure the bearings do not spin in their housings.
I offer the modern version of this bearing, which is still by a top specification bearing manufacturer - NSK (originally Hoffman) in correct '3 spot'\C3 version, however, it is now manufactured using a nylon cage. Although high quality, care must be taken with these when fitting and soldering the bearing retaining plate over them, to ensure the cage is not melted. Other than that, they are just the same as the originals. I will also be fitting them to my own Manx engined bikes in future - I dont think there is much option (Note - one way of lessoning the risk is to lightly solder bearing plate and screws before fitting them, then less heat is required to join them, as they are already 'tinned')
January 2011: I now have this item back in stock with a limited quantity - not sure if they will make any more once these are gone.