Sorry to disagree, but I've seen absolutely nothing wrong with rebuilding Benz calipers. Unlike drum brake wheel cylinders the seal stays put and the piston moves on the seal. You simply take it apart, clean everything up and replace the seal. If the piston and bore are corroded, THEN you replace them. I've taken several apart and have yet to find one not rebuildable. It certainly saves an unnecessary expense to at least check them before tossing them.