This is a dual sided low torque hex bit driver. The parameters for each hex bit socket can be controlled independently, allowing for one driver to fit two different bit sizes. This can also be used as a nut holder.As always, you should use a well calibrated printer. I built mine for use with 1/4" and 5/32" hex bits for working with low torque requirements. The bits should fit into the sockets with little effort, but they should not wiggle excessively. The magnets should be slightly smaller than the diameter of the bit. I used 3/16" ($0.16 US) and 1/8" ($0.25 US) diameter magnets with a height of 1/8". To secure the magnets in their holes, any type of gel glue should work. I used G-Lock BLU-GLU, because I already had some, and it worked well. To finish it off, I sprayed it with 4 coats of Plasti Dip to give it a softer, more comfortable rubber feel.