I made this for the popular cereal box dry boxes, I had tried some others but found my colour indicating beads I got from amazon, many would fall through the gaps, so I decided to design my own, I created it so it is a tight press fit to the bottom of the box on the handle side, this will friction fit it in to the box and prevent it from falling out if the box was tipped over, that’s not to say an impact would prevent it from dislodging, but it's better than being loose. 

The lid is friction fit with a small slot to allow you to open it by inserting a flat blade screwdriver and twisting to create a small gap to then work the lid off.

The window is nothing specific, it's just a 38mm (approx. 1.5 inch) window which I used an old discarded plastic packaging to cut out a disc, and then pressed the keeper in place to retain the clear disc, as long as the clear material is 2mm thick or less, it should be fine.. BE VERY GENTLE AND CAREFUL INSERTERING THE WINDOW KEEPER, THE FRONT DUE TO ALL OF THE AIR SPACING, IS NOT VERY STRONG IN THAT DIRECTION AND YOU CAN PUSH THROUGH AND BREAK IT (ask me how I know)! You can glue the keeper to the body if you think this is a concern but it will be pressed against the side of the box, so unless your tolerances are off, it shouldn't be a concern..

I had also considered adapting the lid to house a hydrometer, i may do that in the future, but i personally just dont see the value in having a hydrometer in every single box when i have dozens of filaments, mostly PLA which really isnt super sensitive to moisture.

Anywho, hopefully some people enjoy/make use of this, it's a 4 hour print for all 3 pieces. on one build plate


EDIT: i made it using Sunlu Spools, just tried it with a Bambu Spool and those must be a little bigger diameter so it is pretty tight, but i did manage to get it to fit.