I needed a fan guard for my 120mm Noctua fan that was going into my Prusa Box.
The original one was just to close to the blades for my liking. I was afraid it would hit, so I added some thickness to it and enlarged the mounting holes. Now it fits like a glove and no worries about the blades hitting. I used 4mm x 16 bolts and nuts.
I printed this so that the grid was aligned with the bed movement so that it would print faster and smoother.
Update:
V2 by request, added a solid grill version, should make printing better.
V3 larger mesh openings for better air flow.
The author remixed this model.