This is an upgraded fan duct for a hexagon / bulldog extruder setup. It is easily attached and removed. It features two distinct channels for airflow, one to the hexagon hot end heat sink, and another directed downward to the build plate for part cooling. In this version, the "downward" airflow area has been enlarged to increase airflow. This has been a great addition to my Hadron Ord Bot. The custom extruder base can be found here: http://www.thingiverse.com/thing:355653 Works like a charm. Enjoy!