This is my first project uploaded to Thingiverse! It is a deck box designed for the Commander format of Magic: The Gathering. There are 3 .stl files, one lower with a window cut out to see the art of the card, one without, and an upper that is used with both. This can comfortably fit a 100 card deck single sleeved with some room for tokens depending on how thick your sleeves are, only tested with Dragon Shield.

The magnets used to hold the lid in place are 6mm diameter with 3mm depth. I used N52 strength magnets super glued in place. Holding the box upside down and shaking it will cause the cards to fall out, but future plans are to design a better interface fit with tabs.

I designed this to change the inner dimensions and magnet dimensions easily, so if anybody feels strongly they can contact me or comment to request a custom fit. I might redesign this in OpenSCAD to allow this customization through Thingiverse when I have time.

Tolerances were designed to work with my Ender 3 and allow easy installation of the magnets (it is not press fit) as well as a good grip on the inner rim.

UPDATE: You will find three new files. These new stl's have a tab system incorporated to allow a tight fit between the upper and lower part of the deck box. This modified design now no longer needs magnets to stay in place, but is preferably in case the plastic wears down. With both the magnets and tabs, the deck box can now withstand the upside-down-shake test, at least in my experiments. Do note you might have to wear down the tabs a little bit to allow for a more easy release if it is too tight for your liking. Once you open it a few times it will wear down to an easier release.

If you are worried about your commander card getting damaged, I've included a outline of a playing card for you to cut out of acrylic. Putting it in between the case and the deck will still allow you to see the commander while protecting it from any sharp edges or points that may try to harm it. There is enough room for both the deck and a 1/8" acrylic cut out.

Update: if you wanted a bigger box for double sleeves, @Willchiv has updated my design. You can find it here: https://www.thingiverse.com/thing:4856922