This shroud takes an additional 40x10mm cooling fan and ejects cool air onto the nozzle and extruded filament. I found that if I printed very fine vertical elements the residual heat warped and melted the model. I also made a thin gasket using thick cardboard to help seal the gap between the fan and the shroud. You could also use that thin plastic/polystyrene packing stuff that comes with disk drives and the like.
It was designed for the Mk8 extruder fitted to a Geeetech Aluminum (Prusa i3 clone).
This version has a mounting hole for a mini-switch that allows you to turn the fan on & off as required. In order to power the fan you should take a 12v source from either your power supply/motherboard or tap into the existing fan supply. I took mine from the "Extruder 2 fan" socket. Disclaimer: I cannot be held responsible if you wire it incorrectly etc. etc.
Print the two parts and glue with Super-glue etc. Line up carefully - there are no locating pegs/lugs.
Note: It looks like the Thingiverse render of shroud shows a hole in the bottom. This is not the case.