I have DRE Oar towers. The top where the oarlock slides in is angled inward. So when I started out with 5/8" split ring, I could not spin the oarlock 360 degrees. This resulted in the split rings getting bent like crazy on the first day. I switched to a smaller split ring for know and the locks will turn freely, but I am thinking there has to be a better way to do this that is both stronger and less of a pain in the ass to take off/put on than a small split ring.