I had an older Schwinn trailer given to me. Because of the nature of the chainstays and the fact that I have disc brakes as well, I was unable to use it. I went to the LBS and bought the square tubing piece that inserts into the trailer frame and fastens to your bike. This one was made by Trek and included the QR and uses a ball socket mounted on the QR so that it works with disc equipped bikes. Oddly enough, the square tubing used for the hitch seems to be of common dimensions for most trailers out there.