Filament sub spools for sample packs

As I recently got 15 filament samples as a present, I quicklyrealized how hard it is to store them efficiently. On regular spools, they would take far too much space, to wind/unwind is annoying, and to print without spool will cause problems.

The following design solves this issue. In short, it consists of a replacement central cylinder for common filament brands ("filament-pm" and "prusament" spools), and a set of independent sub-spools that can easily be added or removed to the main spool. Thus, you can store filament samples on the narrow sub spools, then attaching them to a wide and stable main spool when needed.

I designed two flavours of the replacement cylinder: to fit either the "filament-pm" spools (filament-pm is the company that delivers the "standard" filament at the prusa store - these spool sides can easily be removed from the spool cylinder by pressing four locking tabs) or prusament spools (just pull the sides loose from the paper coil). The "pm-spool" model has a