Bullseye fan duct for 20mm deep fan (noctua etc.)

thingiverse

This is the bullseye duct slightly extended to fit a 40mm x 40mm x 20mm fan, such as a noctua model. By default, it's best suited for a 10mm fan without obstructing airflow. Installing a 20mm fan increases air flow significantly, allowing quiet noctua fans to be used without drastically reducing airflow. Please note that I don't claim responsibility for the duct design. All credit goes to the original creator, whose work can be found on Thingiverse at https://www.thingiverse.com/thing:2759439. I also want to emphasize that I'm not an aerodynamics expert and therefore cannot guarantee optimal performance in terms of airflow or static pressure. However, it appears to function perfectly well as is, despite my modifications. If you're looking for precise control over airflow dynamics, I recommend consulting a professional with expertise in the field.