This part can be added to the printhead of the Ultimaker 2 or Ultimaker 2+, including the Extended versions. The purpose of the part is to improve airflow from the tiny fan that cools the hotend parts. The part spaces the fan away from the heatsink by 5mm and provides a smoother path to direct airflow from the circular fan to the rectangular heatsink. Although I designed this part myself, I got the idea from Torgeir on the Ultimaker forum. There was a previous design that accomplished essentially the same thing, but it seems to have disappeared from the internet. This part is captured by the existing hardware on the printhead, and the existing M2.5x10 screws are used to attach the fan to it. I did not test to airflow improvements, but it doesn't seem to have caused any negative effects. The idea is to improve heat break cooling especially during long print jobs to reduce the chance of a filament clog. In the CAD images, the duct is yellow. In the photos the actual installed part is orange.