Overview:

I designed these bit holders within the Gridfinity system by Zach Freedman.  The 2x2 version holds five standard small plastic bit cases, and the 2x4 holds five small and five medium cases.  Both versions are stackable.

I also designed cases and plugs for bits that did not come with a case.  The design is in Fusion 360 and is fully parametric, so you can customize for different size cases and bits:

https://www.printables.com/model/798817-bit-storage-cases

Print Details:

No supports required.