I tried many available designs from those with bearings that like to unwind the spool on their own. To 3 and four piece designs that required assembly with screws or snap together. I never was really satisfied with any of them because one would work x brands of spools ok but not other and so on.
I thought I would design a simple one piece spool holder that is printed in one shot. Spool holders don't need bearings the spool slides plenty smoothly on the printed plastic, besides you want to have a little static friction or your spool will unwind and tangle. I designed this spool holder to fit all of my spools of filament from small spindles to large, from wide to narrow and should fit 98% of spools out there.