This is bowden type extruder. It is designed to be in a small formfactor, support hard Filaments like old PLA, but also print flexible materials like Ninjaflex. It uses 1.75mm filament. With the opener you can release the stress from the filament to change it quickly.
The Parts are designed to be printed without Supports.
It can be mounted on the outside of your printer with the adapter. The adapter mounting holes are compatible with the Airtripper Bowden Extruder.
Also you could mount it in your Case like in the 3Dator. The stepper motor goes inside and the extruder outside. The material between should be 4-5mm.

See the Printer in action printing Ninjaflex here:
https://www.youtube.com/watch?v=mxCev5Obq2g

You need these parts:
(referral links)

Push fittings 4mm M5:
https://theartoftinkering.com/recommends/4m5fitting/

Mk7 Extruder Gear:
https://theartoftinkering.com/recommends/mk7/

MR105ZZ Bearing
https://theartoftinkering.com/recommends/mr105zz/

608ZZ Bearing
https://theartoftinkering.com/recommends/608zz/

Updates:
24.04.2016:

• Optimised filament channel for better flow.

09.08.2016:

• Again optimised filament channel (works best with mk7 gear for 1.75mm filament)
• added a file with the complete extruder ready to print
• added a hook with a hole to see what your mk7 gear is doing and check if it is aligned (Thanks to 50koruny for the idea)
• added a mirrored version for dual extruders to our github repo: https://github.com/3Dator/3dator/tree/master/stl/extra/extruder_mirrored

23.03.2017:

• updated the tightener to use M3 self-locking nuts (we noticed the squere nuts are too loose and won't always remain in the desired position) You can find the old file still on github: https://github.com/3Dator/3dator/blob/1e32c3fe1a329b2f864e2268b2501e233c2439be/stl/extruder/tightener.stl

22.08.2017:
updated the adapter.stl to be a bit more usable. Now there is also a step file in our git repository.

You can find the complete file history in our github repository:
https://github.com/3Dator/3dator/tree/master/stl/extruder
Here you find the Step files:
https://github.com/3Dator/3dator/tree/master/step/extruder