Vertical Spool Holder with optional Bearing Filament Guide

This is a simpler version of the Makerbot Filament Spool that is only set up for mounting vertically on top of the makerbot. This version doesn't try to grip the whole spool - it's just long enough to hold the spool securely.

Optionally I've added a ball bearing filament guide, mainly because I had an extra 623 bearing from making my "Even more minimal MK7 extruder bearing filament feeder"

There's also a non-bearing version of the guide which I haven't tried, but should work totally fine.