Needed some sort of travel case for some dices.
Ended up designing this one.

It holds:
6x 12mm dices
4x 14mm dices
2x 16mm dices

The top and bottom piece are exactly the same and designed to fit perfectly together.
To keep it closed, I used 2x 4 magnets. Size they were advertised is 6x3mm (But are more closely to 6x2.8mm) The hole should fit both of them.
The tolerance is 0.2 mm for the magnets so it should be a nice pressure fit and otherwise you can use some glue to keep them in place.