This is a holder for a sample spool of filament. Customisable for the hub and spool diameter and the number of arms.
You will need to print one hub and three arms (or as many as you've customised), and screw them together with M3 bolts. I found the holes were the right size to hold the thread and didn't need a nut, but your results might vary.
Drill some 2mm holes in the arms to hold the filament ends.
Update: V2 has fixed a couple of dimension errors I was having, and I've put holes in the arms for the filament ends, angled a bit for a better hold. Also, the arms are looser and I had to use nuts on the bolts.
It's inspired by https://www.thingiverse.com/thing:2033513 but I needed a bigger hole.