Parts printed in PLA using 608 bearings, pneumatic fittings, PTFE tubing and reusable desiccant all inside a Sterilite 28L box. I used weatherstripping to seal the lid (like a gasket) and a $4 hygrometer (just as a monitor, not as an accurate measure). This box has great, built-in latches for the lid. The box is designed to let you use filament without needing to open it to remove a spool. The filament is just pulled from the manifold at the top and fed to the printer. When done, you use push the filament back in and cap it off. I may rethink using the manifold on top - there must be a better way to do that. One side uses M10 Fittings and the other side M6. The box itself uses M6.

In testing, there wasn't a lot of drag from the PTFE tubing.

Use spool holders for all four positions or print 2 of them and 2 intermediate ones and a brace, to save a bunch of filament. The brace prevents the intermediate holders from moving apart. They are screwed together using M3x15 screws.

I wrapped electrical tape around the rollers to give a bit of grip.

Printed on a Bambu Lab X1 Carbon.