Printable push to fit bowden nut-couplings

More details on the Bowden extruder system: http://reprap.org/wiki/Erik%27s_Bowden_Extruder

I just made a serendipitous discovery:
I printed a very narrowly fitting freely rotating coupling and it had such a good grip on the PTFE that I printed another with just a little more contact area. You don't need the nut anymore for the Bowden cable!
I had been looking for push to fit couplings ever since Charles Pax showed me how good they fit to 1/8" PTFE cables. Now it appears that they are defin