I was thinking about a model of a ring that could be folded to provide different sizes. I came up with the idea to take advantage of the retractable mechanism, but twisted into a circle.

The composition of the ring after printing is somewhat tricky:

1/ join the 5 X-es using middle pin (see photo)

2/ join these 5 X-es into stripe

3/ twist the stipe into a circle and join last 2 pins

Although I tuned the model on about five versions, it is experimental and still needs to be fine tuned (gaps, holes, maybe thickness).

Yet it was fun.

Also check out:

https://www.youtube.com/channel/UChKp-968z1i5PN29gbR7YfA

https://www.cgtrader.com/rorys3d