Probably the same size as the Model A, the front one is 2" bore and 2 3/4" long and the rear is 1 9/16" bore and 2 1/4" long. The Mk 1 and 1.5 run to 1430rpm and the Mk 2 is 1800rpm. The bronze bearings are made like er collets, the bore is parallel and the od is tapered. The headstock bores are tapered to match and nuts both sides of each bearing adjust the clearance.