This thing makes it possible to cool down the printed filament so it won't go, like, blob when trying to build something that takes less than 30 seconds per layer, and it will help you building bridges.
To complete this thing you need a 40mm fan, like a chipset cooler, 6 screws, and about 20cm of 2-wire ribbon cable or 40cm normal cable or whatever to extend the coolers power cable.
You need only two of the three wires from the cooler, have a look at RepRapPros Huxley building manual, chapter "Hot end assembly" for what to do. You can wire the two cables directly to a power source or to a special fan connector, if your printer's mainboard supports that.
I used an Akasa AK-210 (that's the one that comes with the Huxley for its extruder, it takes the Huxleys 19V, no problem), unscrewed it from the heat sink that comes with it and reused the four screws to later fixate the cooler onto my thing. (You'll need to shorten two of them with a file or such!) Additionally, I used two short M3 screws that were leftovers from a computer.
This thing does not need support structures to print!