Be careful with these cheapo starter motors.....they are very different beasts from the real thing.
The metal of the casings seems brittle, is a LOT thinner than the real thing and IMO, they aren't worth bothering with.
I've had two of them fuck up on me in a a year.......one from a company in the UK and the replacement was one of these from German Ebay......the second one I still have in the shed and will take a pic or two of tomorrow, but I will not be trying to save any money by getting a cheap one again.
There are loads of parts that you can swap around with little or no problem, (the Audi fuel pump springs to mind) but a starter motor gets some heavy use and there's a fair amount of energy going through it, both electrical and kinetic.......that makes it vulnerable if it's not as well built as it ought to be.