This duct takes the good 40mm Fan Duct V3 from Ultibots and optimizes it to not require printing supports, and to evenly distribute the cooling flow across the width of the gap. It also gives more directed flow toward the printed parts at the end of the print nozzle.Print without support. I printed mine at 0.20 mm on a 0.35 nozzle. 3 perimeters and 3 solid top & bottom layers. The fan mount is taken straight from http://www.thingiverse.com/thing:34387. The fan mount is also the belt clamps. 18 March 2013 - Note: I have sized the holes that mount to the fan to be tapped for an M3 bolt so it does not need a nut. These holes have a 2.5 mm diameter, so if you want to use a nut to hold your fan on, just drill them to the diameter you need. 04 June 2013 - Added v2 stl that makes the exit slots 5 mm longer by request. The width of the slots was reduced slightly to keep the total exit area the same. I have not tried printing this version, so let me know if this version works! 30 June 2013 - Added the stp files of each version (I used the 203 version of the step exporter in Alibre, as opposed to the 214 version. I don't know the difference)