Here is my take on a filament dry box. It uses a 8mm or 5/16th rod(smooth or threaded) and should work with most boxes/tubs that are large enough to fit your filament spool. In the picture I'm using a 20Qt Sterilite box with an 'air tight' gasket and lid latches to help keep the humidity level down. This container is nearly the EXACT same shape and size as the popular Ikea SAMLA box that many people use.
The FilamentDuctInside as well as the RodSlot use m3 knurls and m3 button head screws secure them in place. I think the brass knurls look pretty nice as well!
The Filament duct outside each have a screw in PC4-M6 - PTFE Push Fit connector that couple a bowden tube. I used the ones from amazon sold by Eowpower.
I suggest under sizing the m3 holes when you drill them so that the screws create a near airtight seal.
This design goes with my Parametric Spool Rollers using 608 bearings found here: