Upgraded my Ender 3 to direct drive and needed a different spool holder. I tried a couple and didn't care for how wobbly they were, so I designed my own in OpenSCAD.
Created the oval design first and didn't like the way it looked, then made the rectangular one. These fit very tight in the aluminum profile, but there is no wobble at all once they're in place.
The OpenSCAD file uses both:
2020 Slot Mount SCAD module - https://www.thingiverse.com/thing:1295205
2020 Extrusion Profile for OpenSCAD - https://www.thingiverse.com/thing:4170632
Updated 2022.12.09
I started using filaments that ship on cardboard spools, which don't turn very easily on the support tube, so I made another version which uses standard 608 roller skate bearings. The end caps for the tube are super glued and press fit (rubber mallet). Don't hit the plastic parts directly and be sure to use something with a hole in it (I used pieces of 2x4) so you don't break off the pin for the bearing. The bearings were press fit as well.
No OpenSCAD files available - the new parts were created in OnShape.
Updated 2022.12.27
I don't recommend dropping the roller bearing spool tube on a concrete floor. I sheared off the pins on both ends. Reprinting those parts at 100% infil. Worked fine until I dropped it. :)
Updated 2023.03.20
Still a bit fragile at 100% (yeah, broke another one - don't drop it :) ) so I printed again at 100% in PETG. We shall see. Again, works perfectly - if you don't drop it.
The author marked this model as their own original creation.