M3 socket with quarter inch shaft

Using the sockets 

The sockets do not have a spring mechanism or magnetic holding (obviously), so they will fall out of your bit screw driver, if that has no clamping.

I recommend to use the little watch makers screw driver for this socket, which I had uploaded a little while ago. It features an imprinted spring mechanism and holds the  socket firmly.

https://www.prusaprinters.org/prints/56530 

Printing

This part is very easy to print. No supports or brim is needed. I recommend PETG but PLA should also work.