Ultimaker reinforced low profile external Fan Mount
by ultimac, published
Dual extrusion support requires the fan be offset outwards a little when used with certain fan ducts.
You can also use this design when the fan must be on the same side as the extruder head.
If you only have a single hotend with the fan on the opposite side then you should be fine with the Mk2 version (http://www.thingiverse.com/thing:31599).
Print with support. 0.2mm layers.
Connect to fan duct with M3x10 capscrews.