Perfect fit for 4 standard 1Kg spools using a widely available, affordable, waterproof container from Target and minimal other external components.

Compact footprint as container dimensions of 15.08"/383mm (L), 9.57"/243mm (H) x 11.38"/289mm (W) allow for 4 rolls to spin smoothly using ball-bearing mounted spool rollers with almost no wasted space in any dimension.

Printable Collets to securely hold 4mm OD/3mm ID PTFE tubing (along with caps if not used)

Parts list:

1. Ezy Storage 19qt IP67 Waterproof Storage Box ($10.99 at Target)
   https://www.target.com/p/ezy-storage-19qt-ip67-waterproof-storage-box/-/A-81967133

2. (8) 608-bearings (I use old skate bearings which are widely available and have the advantage of being lubricated with thin oil so they spin extra freely)

3. (1) 12.3/4" (324mm) 5/16"-18 threaded rod
   (a 3 foot version is available at Home Depot for $3.70
   https://www.homedepot.com/p/5-16-in-18-tpi-x-36-in-Zinc-Plated-Threaded-Rod-802227/204274012)

4. Screws to hold spool assembly brackets
   (2) 3Mx8mm
   (4) 3Mx12mm

5. Optional (6) 3mm nylon washers for above screws (more to protect the box from over-torqueing the screw than for air-tightness)

6. Optional (4) ~9mm x 2mm Nitrile o-rings to seal the connector tubes

7. PTFE tubing - 3mm ID x 4mm OD (I used 3mm rather than 2mm to allow the filament to slide smoothly as the amount of humid air that will penetrate any length of thin tubing is small - plus I cap the tubes when not in regular use)
   (I bought 10 ft on Amazon for $8.99
   https://www.amazon.com/dp/B07B8CK8L9?psc=1&ref=ppx_yo2ov_dt_b_product_details)

8. Your choice of silica gel for the bottom of the case - I throw in several 50 gm silica gel bags with indicator

9. Optional, electronic humidity indicator
   (e.g., 6- pack available for $9.99 at Amazon https://www.amazon.com/dp/B096R9LSX5?psc=1&ref=ppx_yo2ov_dt_b_product_details)