Printrbot Plus v2.1 Filament Holder

This filament holder is designed to sit on the 12mm z-axis rods for the printrbot plus v2.1. I originally looked at the ones on Thingiverse, but the one I found seems like it was designed for 10mm rods instead of 12mm rods.

This is my first attempt to use OpenSCAD / design my own object.