If you want to store your filament spools vertically without them rolling off your shelf, this is the gadget for you.

It's compact and only takes ~10g of filament to print.

You can slide it apart to fit spools with 4.5cm - 10cm of depth.

This holder does NOT allow the spool to roll; use it for storage only.

Printing instructions:
Layer height: 0.2mm or lower.
Shell thickness: 1mm or higher.
Infill: any.
Build plate adhesion: optional. (If you decide to apply Brim, make sure to remove it thoroughly from Part 1 so it can slide into Part 2)
Support: not required.