Effective Fan Duct for Prusa i4 (include Tests)

This thing full compatibility to:
https://www.thingiverse.com/thing:2182105
https://www.thingiverse.com/thing:2332049

I tested by two test models
https://www.thingiverse.com/thing:58218
https://www.thingiverse.com/thing:1879347
or try yourself https://www.thingiverse.com/search/page:1?type=things&q=overhang+test&sort=relevant
Print with PLA, see images.
It very effective up to 10 degree from bed.

#### To assembly duct need
- M3\*4\*4 nuts (to fuse in plastic) - 2 pcs, like this htt