Handle for 3mm Allen key.
It is very useful when assembling prusa i3 MK3.
The 3mm Allen key fits perfectly into the handle.
Maybe you need a oil when put allen key into the printed handle part.
I recommend a zip tie in the Prusa i3 MK3 kit, but it's okay if you have a proper zip tie.
Using a 1.75mm filament, apply oil to the inside of the hole
and assemble the allen key.
If you don't use oil, you'll have a hard time assembling it.