Ball-joint filament guide

Am using a TUSH-style filament spool holder (https://www.thingiverse.com/thing:2706687) which apparently works TOO well, as it allows the spool to rotate backwards as well as forwards (when the extruder retracts).

This rocking motion causes the filament to become loose and unwound - sometimes causing the filament to form a knot and seize up.

The filament guide keeps the filament from whipping around and I quite liked the ball-joint ones, as it allows full 360 degree motion (well its a cool design too!)

I've remixed this one to fit a 2040 aluminium extrusion and be 40mm from the rail