Update 2:
-Added mini version without angled base: 30mm shorter than compact version and 6mm narrower, still works for standard-size spools

Update 1:
-Added 10mm shorter version with thinner+angled base
-Increased tolerances for connecting bar

This is a minimalistic, streamlined spool holder designed in a retro style that has an integrated filament guide, prints in only 2 pieces, and doesn't take a lot of material to print.

I designed this filament holder because I needed a more reliable way of feeding filament while printing but the existing designs I found either used too much plastic or needed additional components, like bearings and bolts. Because of this, my spool holder is designed with the KISS principle in mind, for lower cost and greater accessibility.

For standard and compact size:
Print 1 base.stl or base_compact.stl and 1 bar.stl.

For mini size:
Print 1 base_mini.stl and 1 bar_mini.stl.

If your spools of plastic have an unusually large diameter, print the compact or standard versions. The standard version looks better at larger layer heights due to the flat (non-angled) base.

The mini version is suitable for most spools with a ~200mm diameter.

I printed the spool holder with 1mm shells, 0.6mm top/bottom thickness, and 15% infill at a 0.2mm layer height. The bar was printed at the same settings except with 10% infill.
Print in the given orientation without supports. A print fan is recommended due to the overhangs in the model.