This is the single row roller bearing as fitted to both sides of the SOHC Walter Moore CS1 and CSJ 1927 - 1930 engines. It was also fitted to Model 18 engines of the same period. These are the correct original 'C3' looser fit bearings - but are from a slightly lesser quality NKE brand (i.e. not RHP Brand). See listing for more detail
Update Jan 2022 - In previous years, we have been able to obtain this bearing in UK quality RHP brand. However, RHP are no longer manufacturing the C3 fit version of this bearing - therefore as an alternative - we are now able to offer NKE Brand 'C3' Fit alternatives. These are an offhshore brand - and not of quite the same high quality as original RHP . . . but is ultimately how it will go with all the main Norton bearings, as original RHP brand run out. These bearings are still of a reaonable quality, and unless you are still riding your bike 20k miles a year . . . should be fine! (and are of course much cheaper than any 'new old stock' RHP brand versions we are still able to find.
Backround Information on C3 or Standard Fit bearings:
These 'standard fit' bearings are exactly the same manufacture as the C3 versions, except when fitted they have a less loose tolerance - so if you decide to fit them, bear this in mind and allow for it when first running them in (however, many people historically did not realise there were different fit bearings - so you may find your engine has already been fitted with standard bearings by a previous owner. Original C3 bearings will normally have either C3 stamped after the main bearing designate on the outer race, or 3 dots (i.e. '. . .'), which was often the old way of showing them as C3 fit.
Final point on ball and roller main bearings fitted to 1930's/50's OHV and SV engines: Unusually, Norton's showed a roller bearing being fitted on both sides of the crankcases on OHV/SV engines (i.e. 1948 catalog), with a ball bearing fitted just on the outer drive side. However, I have stripped OHV engines down in the past where a ball bearing is fitted both sides, with just the drive side inner being a roller bearing (as was the case with all SOHC engines). Not sure if it makes a great deal of difference - as like the SOHC engine, the OHV/SV engine was locked to the timing side bearing - but worth noting if you are struggling to find two roller bearings (and once ours have inevitably ran out)