The problem (or at least the first and main problem) is that the leather O rings are not available anywhere at any price. You will have to custom fabricate them for your horn, a very time consuming and expensive process. The next problem is that once you get new rings installed, these horns are really a bitch to deleak. Again, a time consuming and expensive process. The final major problem is that there are only a handful of technicians with any experience whatsoever with these instruments. Joe Sax is the best bet for one of these. He's done quite a few. I haven't done one in at least 20 years, and have no desire or the time available to take one on.