Summary I started learning a new design software by today and these files were the result. I can highly recommend Designspark Mechanical (http://www.rs-online.com/designspark/electronics/deu/page/mechanical) and CraftWare (http://www.craftunique.com/craftware) which were used to design and print! It is supposed to be placed in an groove mount compatible extruder and to carry a nut which holds an 4mm bowden tube in place. On the gallery image you can see this thing fits nice in a gregs/wade extruder from Jonas Kühling:http://www.thingiverse.com/thing:18379 Design with Designspark Mechanical Sliced with CraftWare .2mm Layer, .42mm lane width, smartABS by Obritech. Printed very well without any support.