These are the unions that screw into the crankcase behind the timing chamber - it is the smaller 1/4" BSP side that screws into the crankcase, the larger side is 3/8" BSP and takes the distinctive large oil pipes fitted to Norton Internationals.
As with the smaller breather union, we also offer a cheaper modern alternative using modern AF spanner sizes on the hex, but the hex on those are larger - while the version you see listed here are copied from a pre-war orignal and are made with the correct Whitworth Hex spanner size and indistinguishable from the original.
I have to say that I have seen SOHC crankcases with original unions both in plain brass (like these) and cadmium plated, but I know the pattern we used for this type came from an original engine and was in plain brass, and did not have chamfers on either end of the hex (unlike modern equivelants which has a much larger AF hex, does have chamfers, and has a more modern looking cadmium plate finish) - so these brass versions shown here I think look much more correct. Sorry they are not cheap compared to modern AF equivelant - but they are CNC machined by us - not a mass produced modern version.
Fitted to all SOHC Engines (and I believe also fitted to DOHC engines as well), with two fitted per engine (price is each). We also sell the correct high quality wide red fibre washers to fit these and ensure they do not mark the crankcases