Fits ANY spool. Up to 1Kg as is (see photos), scale up for larger spools (see "Larger spools" section).

Can be printed on a Mini 3D printer. Prints in one piece, pre-oriented, zero assembly.

Option to pass the filament through a guiding hole.

Print settings 3-4 perimeters 20-30% infill Material: PLA is more rigid with less friction, while PETG is less brittle.

Larger spools Scale up depending on printer and spool size: For 2-3Kg spools (up to 300mm diameter) scale up to 128%. If it won't fit your printer, try scaling it less on the Y axis (using non-uniform scaling). Scaling Y to 125% will fit an Ender3, while keeping X and Z scaled at 128%.

I prefer storing all filament in dry boxes, but this is my next best option.