This keyring was designed because I really liked my older, larger Fidget Gear Keyring, but found that it was a bit too big to use as a day-to-day keyring.
This keyring features a similar design, but only uses two gears, and both are the smaller, 15T 15PCD gears.
Updated 22/06/16: added STL's of the 15T gear with larger centre bore based on feedback that the holes were too small. There are now centre bores of 5, 5.4, 5.75 and 6.5mm. My testing shows that 5.4 and 5.75 work the best depending on what printer you use.
Assemble the keychain using two 12mm m3 bolts and two m3 nuts.
For ease of turning, I also used a sharp 5mm drill to re-bore the gears at high speed to give a smooth surface inside the bore, and also used a scalpel to clean up the axle shafts from where printing the circular layers left small ridges.