If you want to remove items like USB flash drives, key fobs, or other key chain-bound tools without fumbling with key rings, print my key chain separator. These devices are typically made of metal, cost around seven US dollars on Amazon, and separate with the push of a button, like this example. My version of the key chain separator is designed to be fully 3D printable without support. Rather than a button push, the pieces of this device separate with a twist and a pull--motion that is uncommon even in stuffed pockets. A simple locking mechanism means that it should only break apart when you want it to. If you need more key rings, consider printing this thing, where the "Rr" parameter is the ring radius and "Ccr" is the ring thickness..

Update on 2-9-18

I have fixed the part clearance to provide some extra room for inconsistencies of printing and discrepancies between printers. The result is a slightly looser fit, but less required post-printing and hopefully more accessibility no matter the tolerances a user's printer is capable of.

Update on 2-18-18

I further improved the fit of the two parts. Be sure to set your print resolution to 0.15 mm.

Enjoy!