Summary

This fits into any standard CD case with room for a single minidisc. Disc fits perfectly into opening but is not a tight fit since cd case snaps closed to hold it in place. If you want it to be a tight fit it would probably only need a piece of tape on the inside edge to make it snug.

Printing:
Example printed with prusa slicer "Draft" setting - 20% infill, .3mm layers with 2 layer perimeter and 3 layer top/bottom.