Mini Ratchet for Bits as a Key Chain.

thingiverse

You'll Need One Pen Spring! A mini ratchet for bits makes an awesome key chain! It requires just one pen spring. The 100% size sits perfectly on M3 nuts, which have a diameter of 5.5mm. For the 110% size, it fits seamlessly with bit screwdrivers. To make printing easier, we've included a .stl file that breaks down the body into separate parts for later assembly and gluing together with another adhesive.