chain link ?

Lube up inside the link, then get it all put together with the Orings and such, and then if the master link won't get tight enough for the pin, use a pair of vice grips as a vice to clamp the master link down tight. Use two pairs of vice grips, one on each end. Once you've got it where you can see the groove where the pin goes in, pop one end off and slide that pin (or whatever it's called, clip, etc.) on there.