The R87F-FG120: Mounts directly over the fan's intake or exhaust face — typically four screw holes line up with the fan housing. No special tools; just a screwdriver and a few minutes. The finger guard keeps the enclosure's IP rating intact as long as the fan itself is guarded; it's not a filter, just a mechanical barrier. If you're swapping a damaged guard on a live panel, kill the fan circuit first — the guard stops fingers, not spinning blades.
Part number is R87F-FG120, as printed on the box and the part itself.