Three UNF nuts which secure the crankshaft extension to the flywheel studs on a Lister SL1 type engine. 

These are high quality Grade 1 nuts of the correct 1950s thread, not modern metric. 

As you can see from the photos we have tested these on our SL1 so you can have confidence they fit.

Please see my other items for more fasteners for Lister Ds, Petter A1s, Bamford EV2s, Ferguson 20 & 35 tractors and Ferguson Ploughs.