This is a mod of the Ultimaker 2 that moves its extruder on the top of the feeder:https://www.youtube.com/watch?v=AafTbwCPI98It is intended to try reducing the underextrusion problems (see http://umforum.ultimaker.com/index.php?/topic/3261-ultimaker-2-extrusion-problem/page-2)You have two parts to print:- The block.stl, this part binds the extruder on the top of the feeder.- The tube.stl, this part is a guide tube that goes inside the feeder, because the guide tube will now enter in the filament pusher box on the top, and not on the back