Two of the four retaining rings were in the box. I was able to install one, but the other broke when I lengthened it to fit over the end of the stock. I had a spare part in my hardware collection and now it works well and actually seems to do the job it's advertised to do. We need to check who collects these things. Most people don't have the tools and parts to install these clamps. I would recommend using press nuts instead of these snap rings. Sorry but I'm an engineer.