I accumulated some spools with only a little bit of leftover filament, to avoid wasting space by keeping them on big spools I wanted to print smaller ones. I ended up making my own model and made it parametric so that I later could print them in any size I want.

Strengths of this model:

• Parametric, to easily make it small for example
• Easy to lock/unlock (with no tools or hardware) when needed but stays put otherwise
• Is compatible with regular spool holders and acts like a regular spool

Printing info:

• Print both parts separately with tree supports for the hanging part of the locking mechanism.
• Watch out that the seams don't line up with the walls of the locking mechanism to avoid weak spots.
• Once printed square up the locking parts with an exacto knife if needed and then simply line them together, press and finally twist to assemble the spool. After this the pieces will be locked together but you can still easily separate them whenever needed.
• Would you want to use one in a heated drybox, keep in mind the max temperature of the filament you used to print this spool! I would suggest printing it in ASA to cover most needs.

The design dimensions are based upon an eSun spool and the locking mechanism is loosely inspired by those of Bambu lab