I am very happy with a brand of filament that happens to have spools that don't fit my 3D printer (here: https://www.youmagine.com/designs/reprap-leeuwenhoek-v1)now I can buy this cheaper material and respool my empty colorfabb spools easily. This design works well with many other, but not all spools.As always, feel free to modify the idea to fit your needs