Low Profile Spool Holder

Low profile spool holder for 2020 Misumi extrusion, similar in design to the [Kossel compact Filament Spool Holder](http://www.thingiverse.com/thing:312624) which inspired this version (Thanks Elliot for the suggestion). The spool fits over the small hub, and the hook drops in from the top to hold the spool in place. The hub is small enough for Taulman's mini spools, and short enough to fit in the stepped spools from Ultimachine and Atomic Filament.

Requires a 10mm OD, 5mm ID, 4mm wide bearing and a 20mm M5 screw.

There are two hooks, the magnetic spring hook is designed to be printed in a magnetic filament, with 5mm magnets in the insets. The regular hook doesn't require magnets. Press the sides of the hook while repositioning. I don't think there's any real reason to use the magnetic version, I just wanted an excuse to try out the magnetic iron filament. This design has enough resistance to prevent the spool from unwinding on its own, at least with the spools I've tri