M2 bowden drive

This is the bowden drive for my dual e3d hotend design found here.
http://www.thingiverse.com/thing:824403

There are 2 versions of the part. The 1b1 version is still designed for the tube holders that came with my e3d hot ends bowden kit. They are pass through 10 mm thread types. Which means that the tubing can go all the way through the holder. I put stops in the passage that will prevent the tubing from being sucked back into the extruder gear when it retracts during printing. The larger 10mm threads of these connectors are almost to big.

The 1c version is designed for some air pneumatic 5mm thread Dia 4mm hole brass quick connectors that I got off ebay. These are what I am using now with success.

Update #1
I was having some issues when using retraction and thought it was because the geometry of how the gear lines up with the bearing. I made a few modification to the geometry and also reduced some of the plastic needed by creating a few voids which have so far not had an