I loved The Goofy's loose filament spool, but it was too big for my MakerBox samples. I remixed it to be small enough to fit the samples I get every month.

The Goofy's one fits a 140mm diameter filament sample at its smallest.
Mine fits a 120mm diameter filament sample at its smallest.

If you want to remix it further, here's the original source:
https://cad.onshape.com/documents/089e529c90917805ec38b932/w/17611d521d83673cdb1f35ed/e/3f5446c54370a7400d0707ea

I didn't want to go smaller as I left the interior hole small enough to fit over my autorewinder spool holders.

Note the orange one in the same photo as the silver one is the original Goofy one, shown with the silver one for a size comparison.

Goofy's loose filament spool is here:
https://www.thingiverse.com/thing:1986210

Print instructions

Category: 3D Printer Accessories Print Settings

Printer Brand: Prusa

Printer: i3 MK3 MMU 2

Rafts: No

Supports: No

Resolution: .2

Infill: 15%

Filament: Atomic Filament, Hatchbox, & MatterHackers PLA Orange, Yellow, & Silver
Notes:

I printed this with both a .6 and a .4 nozzle and it worked fine either way.

How I Designed This

Designed using OnShape:
https://cad.onshape.com/documents/089e529c90917805ec38b932/w/17611d521d83673cdb1f35ed/e/3f5446c54370a7400d0707ea