I made this box for the awesome Math Spinners by 3DogPrint ) Multiplikations- und Divisionsfidgetspinner von 3DogPrint - MakerWorld ). I didn*t need a closed case, just something to keep them organized in the classroom.
The box is 85mm on the inside. So it has room for 8 Spinners with 5mm of tolerance.

Just adjust the space in the slicer for a tighter fit or to accomodate more Spinners (10mm per Spinner)