Dang, now I can't remember. I know my original non o-ring chain that came with the bike had a master link, and I was always worried because it would come off all the time. This chain is an RK size 520 o-ring. I am embarassed to say that I lost my master link when I can't even remember if it had one. I remember that because of the o-ring, I had to really clamp the hell out of the master link to get it to pop on there when I first put it on the bike. But since then, like over a year ago, I've never taken it off. I didn't notice any of the rivets being noticeably longer, like there was a masterlink missing. I guess I was just looking over my bike closely tonight and realized there was no masterlink. Does anyone else with an o-ring have a masterlink clip? I also used one of my automotive brake spring pulling tools to pull the exhaust pipe spring off, like someone mentioned in another thread. Works well. :cool: