I have 10 of the NFM now. They are great portlights.
However, I also got their flyscreens, and that was a mistake. They are a PITA to fit, and the rubber-on-SS junction on the external side causes oxygen deprived SS and thus rust stains. The mesh can develop rust stains as well. Sure, it all cleans up OK and with colinite metal polish lasts pretty well, but I would suggest making custom internal (velcro?) screens.