This is a small baffle for a 40mm fan mounted on the side of a prusa x-carriage. It directs half the fans air down over the plastic at the nozzle. My fan is mounted between the rods and slightly up so that it's bottom edge is 3mm up from the plane the end of the nozzle rides at. Half the air from the fan cools the top of the hot end barrel to protect the plastic in the Greg's extruder. This directs the other half of it's air down below the hot end and cools the print. I've seen an immediate benefit in print quality with the directed cooling. While printing this part, I had to manually fan it during the sloped part to keep the print clean. Slowing it down to %50 speed during that slope also helped to make it a nice clean plane.