Grill for 50 mm fan

This nicely designed piece by Sterling prints much better upside down. The original either leaves a coarse inside with lots of strings to clean up, or needs support. The height has been reduced from 5 mm to 3, since the clean print needs less tolerances against the fan blades.

This cover is universal and should fit any standard 50 mm fan with 40 mm hole spacing, not only for the Ultimaker.