Customizable magnetic case for holding lens filters or other similarly shaped objects. The magnets work as a hinge, and to hold the case closed. If the cases are the same size, they will also stack nicely, with the magnets holding them together..
Check out the diagram in the photos section for a description of the customizer parameters.
Use cylindrical rare earth magnets for the hinges, around 3-5mm diameter and 2-4mm in height (depending on the thickness of the filter and how strong you want it. You can use http://www.thingiverse.com/thing:42800 to get the diameter right for a good press fit, or make them a bit oversized and glue them in. Make sure to orient them properly (so they attract) before pressing them in.