This felt wheel bearing washer is marginally bigger than the main wheel bearing felt washer (our Item 0311) and I believe was of the type fitted to later metric type wheel bearings (which I think were fitted on later 1960's onwards bikes). This larger type wheel bearing were also fitted to some conical racing wheels - and the bearing shown here with that felt washer is a roller bearing to fit a late Gardengate/Featherbed Manx Norton 'Conical' rear hub.
The difference between this felt and Item 0311 is only marginal, but if you are using larger wheel spindle spacers, this felt gives a little more room. The internal diameter of this felt is 25mm (compared to the internal diameter of 15/16" of the normal Norton wheel felt - Item 0311).
However, I have also found this slightly larger felt washer to be a good size fit over the tapered SOHC Norton crankshaft. This can be useful to fit if you have a competition SOHC machined with open primary chain on the road or track and want to stop dirt from the road and oil buildup behind the sprocket (but if doing so, make sure on fitting it does not get trapped under the sprocket taper, which may stop the taper being fully effective on the sprocket). Also useful, if you have some wear on the driveside crankcase bearing housing inner face to crankshaft and having some oil leakage there. Note: if using an Inter or magnesium crankcase with the normal roadgoing Norton Oilbath chaincase - then a felt here is not necessary, instead, an oil resistant gasket should be used between the large flat crankcase main bearing housing an the inner oilbatch chaincase