Both the front and rear hubs were the same as Mark hubs - just the brake drums were different. The front drum was, of course, larger in diameter. The rear drum was the same as a Mark, but had the bolt-on sprocket. The rear brakeplate was slightly 'beefier', and whilst looking like a mark unit, had an operating cam with a slightly larger shaft, and the boss on the brakeplate was drilled and tapped from the rear for a grease nipple (the Mark had the nipple in the end of the cam spindle). If you come across a rear drum, make sure it is for a 'Plus' - the 'Comp' had the same setup but the sprocket was offset more to the outside.