With something as simple as a caliper, I'm often surprised at how few people repair leaking or frozen calipers. I had a set of rebuilt calipers that I bought, it was a new project and I had no cores and I had one caliper that was stuck. Remanufactured calipers are about $60 each. There were far fewer such repair kits. I pulled the calipers out and found that the area between the boot and the piston seal was rusted just enough to prevent the piston from sliding freely. A quick sharpen, some cleaning and reassembly and I was back in business, $100 cheaper than buying remanufactured calipers. I'm glad there are still companies that offer kits that let me do the job myself and save a ton of money. I also find that I pay much more attention to detail when I do the work myself.