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I'm not sure what to search for, and I'm hoping you can help me find whatever this might be called:

I'm looking for something that looks like a keyring, but expands with pressure if pressed onto a tube; it then squeezes when released. Maybe think "metal rubber band".

It needs to be metal for electrical conductivity, ~1mm in thickness, and about 2-3cm in diameter. (I've scoured Amazon's keyring selection, but everything looks far too strong to expand and bounce back.)

What would something like this be called? Other ideas?

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It depends how much it needs to open/stretch.

External circlips/retaining rings spring to mind - they're normally installed into a groove, but don't always have to be. Getting them out of a groove (and sometimes in) takes special pliers, but just used on a tube that shouldn't be necessary.

Circlips, via Wikipedia

Retaining rings image from Wikipedia https://commons.wikimedia.org/wiki/File:Axial_Rings.jpg

Otherwise 1-3 turns cut from a suitably-sized compression spring should work. You can either buy springs or make them by wrapping wire round something undersized. Piano strings are a good type of wire for making springs.

The actual effect of squeezing in one direction to expand in the other requires a more complex braided construction. Braided sleeves in (tinned) copper or steel are conductive, but will fray unless you seal the ends.

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  • Thanks for the answer! FYI to others who might find your answer: these are also called "External Retaining Rings" or "C-clips" or Circlips. E-clips are different, but could be useful depending on the task. In my case I need "overlapping external retaining rings" for a rotary electrical contact, but haven't found any yet.
    – KJ7LNW
    Commented Jan 7 at 23:07
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    Another term of interest is slip ring - that's more like what you're trying to end up with but might give you some pointers
    – Chris H
    Commented Jan 8 at 7:01

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