First!

Be sure to print out the tolerance tester first.
The size of the bit heads is quite different, even if it seems standard at first, and the tolerance it can also depend on the setting of the printer, the accuracy and the material chosen.

In any case, the tolerance size you choose should be comfortable for insertion and removal, but not loose

Second!

Print it out, and glue it the magnet inside. If you want the cap to roll off less easily, use an o-ring.

Tip!
If the set of bits is not uniform at all, then a slight sanding of the edges can help to remove enough from the bitheads to be able to use them comfortably. You don't need to sand a lot.

BOM:

• Magnet 5x2mm
• Bithead
• O-Ring (Optional)
• Key Ring (Optional)
   

Print settings

• Material: Several Type Petg/PLA, but i think Petg better choices.
• Nozzle: 0.4mm
• Layerheight: 0.2mm STRUCTURAL
• Perimeters: 4-5
• Support: No (Only Cap, if you want, the inside comes out a little nicer.)
•  

Essentially, the idea, and magnet and o-ring etc is from here, but this is not a remix.
[https://www.printables.com/model/606404-mini-bit-driver-keychain](https://www.printables.com/model/606404-mini-bit-driver-keychain)
Thanks Man!