This is a minimal fan duct for the PolyStroooder Tri Hotend, to be used with a 25mm fan instead of the normal 30mm one. I use a high effect Sunon fan, that is both effective and quiet. My effector can be found here: https://www.youmagine.com/designs/heffabot-polystroooder-effectorFor the part connecting the fan I used DoomMeister's "Fan Mount/Duct - OpenSCAD Library" found here: http://www.thingiverse.com/thing:18273