Two-piece ring that clicks together and apart or rolls around. Fun little fidget toy.
 

There is a gap so even printers with bad tolerance can print it without an issue (mine has bad tolerance so I know)

I originally made it to test a snap-fit design to hold up my chair because the pneumatic lift stopped working. The chair part is pretty much just a 111mm tall version of this with three snap-fit connectors. once I made the prototype for it, I found out that it was very satisfying and thought that I would just post it.