Fan duct Geeetech Prusa I3 Pro B

I designed another fan duct before, but this didn't work as good, so I did this and this is awesome. Designed for 40 mm fan (files without diameter in name) and 50 mm fan.

Update 2017-07-22: New version (v4) for better cooling results. At the inside I added some baffles and a cylinder under the fan for better air flow. I will add a version (v5) without the cylinder, because if you use a fan with other plate diameters it will harm the air flow.
Version v6 is with an extra outlet at the middle