Picked up some rear B5 S4 calipers for my B5 A4 today, Planning on doing a 325mm rear BBK. The calipers are in ok condition but the rubber boots are a bit busted.

Does anybody know of a good wright up ? Is it as easy and straight forward as just twisting the compression cylinder out and replacing the seals ?

I dont know what brand calipers , but from what i have seen it's harder & harder to get rebuild kits. Most of the kits that are available just have the seals & no pistons. If the boots are torn when these calipers were on the vehicle there is a good chance the pistons are rusted or pitted also. best to send them to a rebuilder.