A filament pulley used to guide the filament from the spool into the extruder.Print the pulley parts and clean up the support in the ball bearings so that the balls can rotate freely. Print the holder parts. Click the pulley parts together and glue the holder parts (as described in http://www.thingiverse.com/thing:6919).The openscad file uses the ball_bearing.scad file from http://www.thingiverse.com/thing:40559, you will need that file too if you want to render this thing new to stl files.