This is a remake of the fan duct for cooling the E3D Hot End designed by euphy and available at http://www.thingiverse.com/thing:120249 I tried the original one with my v6 hotend but one side of it was too close to the source of heat and melt at some point, this is why I change its geometry a bit to make sure it far enough to prevent any damage. I use this with Greg's Wade extruder on my Prusa i3. Enjoy )you'll need to use screws to connect your 30mm and 40mm fans or you may use M3 bolts like I did, no nuts needed with this design.