This is a Dremel Bit Holder.

It is modular design so that you can print as many as you need and clip them together.
It has pockets at the back so that you can glue 3mm magnets and hang it on a metal surface in your workshop.

The sockets for the bits might be a little tight depending on the print settings and nozzle you use, use some heat and a bit sample to open them.

There are two designs to choose and the Sketchup file so as to modify them as you want.

Best of luck!