Rebuilding Kelsey Hayes front disk brake calipers?

It's probably time to rebuild the caliper. In addition to the rubber 'bellows' on the outside there is also a rubber "O" ring inside that seals the piston to the housing. These are hard to replace because usually the pistons and bores are heavily rusted and corroded leading to boring and sleeving the calipers and replacing the pistons. I prefer to let professionals rebuild them so they can provide whatever is needed.