The best way to write the contents of the storage bags/boxes/etc. you put to your freezer is to use the thinnest painter's masking tape - they will stick and hold properly in the -18 ℃ environment. The STL was generated to hold 2 pcs of 20x10x5 mm neodymium magnets inside but the Fusion 360 design is parametric so you can customize it to the magnet(s) you have.