This model is a handle for 4mm screwdriver bits. It is based on my blade handle and uses a mandrel system to hold the bits in place.

To build it you need a 25mm M3 screw and a melt insert. Print one "handle", one "Knob" and one "mandrel".
There are 3 types of mandrels depending on the diameter of the melt insert you have at hand and 5 types of knob. The difference between the knob is just the small symbol meant to represent the type of driver head. If you don't care you can just use the unmarked one called simply "knob".