This filament holder was designed using openscad; in this version it fits into Ender 3 Pro, and uses bearings 7×22×7; but it is fully parametric, so you can change every measure. It is designed so that both large and small spools can be mounted (inner spool diameter 40mm). The rotating cylinder is slightly "hour glassed" so that the spool will stay in center. I recommend printing with a strong material, such as PETG (as in pictures). I printed it with standard Cura settings (20% filling) and supports (but not for the nut).