My 25mm extruder fan went out. I created this from cardboard first, it worked well enough to print this shroud out. I cut it in 2 parts, you can glue them together. I printed with support. This works well. It clips on fairly tight. I did not screw it or glue it at all. The only thing I did do, was use some aluminum tape (for duct work) to fasten the fan to it, as well as a bit right near the hexagon extruder for heat dissipation purposes. It is the same plastic that the extruder melts after all. Print with line support and glue the 2 halves together. Finish with aluminum duct tape for best cooling performance.