Prusa i3 Fan Duct for J-Head & Wade - Improved Ver. 3

This is an improved variation of philsson's 40 mm fan duct. http://www.thingiverse.com/thing:184055

There is now a bit more height at the two screw mounting slots.

I improved the air flow in the duct again, by creating a transition between the main plenum and the ring duct. There should be even more air flowing to cool the extruded material now.

I've also directed the flow of air around the nozzle a bit better. I had printed a few big herringbone gears for a Wade style extruder and they