Summary

I wanted very light covers for my fans, so I've quickly designed this one. It seems not to disrupt the inner airflow at all, and prevent me to put my fingers in the blades, and protect my fans' holes when I screw too quickly.

2 versions are provided: 30x30 and 40x40.
Not the best thing in Thingiverse, but I'm happy with it. :)

Tips: As it also very thin, you can easily sanding it by applying a finger on it and move it to a sanding paper sheet.

Edit: After 6 year using them, the PLA used is very tired, so I wanted to re-print them.
I saw there were not optimized for printing (rounded... I was unexperimented) so I did a simplified (and a bit stronger) version.
If you look the model, it can be less beautiful but in reality, except if you add support and fine layers you will not see differences.
This V2 version doesn't need to be sanded and should be more resistant. I also use PETG now.