Compared to my first attempt, this is a much more user friendly filament dry box system using the Sterilite 20qt storage boxes. No more removing all the spools just to change out one.

Note: I was informed that there are at least a couple Sterilite 20qt containers. This thing, with the drill template provided, only works with the gasket sealed one.

For the filament caps see my previous version here: https://www.thingiverse.com/thing:2849767

All parts print without supports in the orientation provided.

EDIT: I went back and tweaked the sizing of the spool rollers and the rod holders to accommodate up to 75mm wide spools in all 4 spots. Print 16 halves for a full set. (You can find the old STL and STEP files in the Previous_Version.zip file).
Print 8 of each size spool roller halves then glue them together to make 70mm and 75mm rollers. These sizes are the best compromise I could come up with given the width of spools I've used and the available space in the 20qt container. The 75mm width fits my Atomic spools and the 70mm fits just about everything else. The only spool I'd have to span two rollers would be an original Prusa spool that came with my MK3.

Install regular 608 bearings into the ends of the spool rollers. Almost all of the bearings I have here slid onto the linear rods just fine but a couple were too tight of a fit so your mileage may vary.

Use 330mm 8mm diameter linear rods for the spool roller supports. These are the same size as the Prusa MK3 Y rods and is also a standard size available on Amazon.

Use the drill template to mark the rod holder holes and drill out with a 3mm drill bit. Install with the T on the rod holder parts facing up and use M3x12mm screws and M3 locknuts.

Fully assemble the parts onto the linear rods before securing in the box.