This part mounts a 30mm x 30mm x 10mm fan to the side of the Printrbot Simple extruder to cool the filament as it enters the hot end, preventing those goopy jams on long prints.The extruder motor on my Printrbot Simple gets hot enough on long prints that it softens the filament before it makes it to the hot end and causes these irritating goopy filament jams. This part mounts a 30mm x 30mm x 10mm fan to the side of the extruder to cool the filament, replacing the M3 35mm screws holding on extruder motor with M3 40mm screws, and then the fan mounts to the part with M3 16mm screws. I mounted an Orion OD3010-05HB fan, and connected it to the 5V power on the E-Stop connector on the Printrboard. I'd like to move it over to the 12V power supply (and switch to the 12V Orion OD3010-12HB fan), but I couldn't find an easy 12V tie-in point on the Printrboard. I'll switch the fan to the 12V side when I get motivated enough to splice some wires, but in the meantime the 5V side seems to be handling the extra load just fine.