This mounts under the laser-cut parts on a Printrbot (I'm using it on a Simple) to hold a 40mm fan. The bottom has two hex indentations sized for the 6-32 nuts that attach to the two 6-32 screws used to mount the extruder.
Use the existing 6-32 screws and nuts to mount this under the extruder. There is a curved opening so you can slip it over the hot end. Use two M3 20 screws and nuts to hold the 40mm in place.