Small spool for filament samples

I had gotten a bunch of ColorFabb samples to use and I wanted an easy way to load up the 50g samples of filament onto a spool without laborous winding. Basically, remove the side, drop in the hoop of filament, hook the tail end, screw the side back on. You may need to tighten or loosen the coil to make it fit the spool. At least that's far easier than rewinding the filament.

The center is for a 8mm rod. I've enclosed CAD sources for those that want to alter it for other rod sizes. It could us