These are the printed housing of the new Printrbot Gear Head Extruder. Keep checking in to this page as more iterations are to come. 2/6/15 - just released v0.03.  A mashup of the gear head extruder and the alu extruder.1/18/15 - just released new iteration v0.02.1 - from Tjb1 - fixed holes in previous STL 11/11/14 - just released newest iteration v0.02