What annoyed me the most was the leaflet inside the company, a photocopy of a photocopy that was already finished and the ink was also fading! I can't make out anything it says, it's unreadable, and I wanted it to know the scales for the filters so I can buy the right replacement next time. Now I have to search for the ratings on the internet.
I don't use the mask for extended periods, for simple use it's fine and the most important thing is that it doesn't fog up my vision glasses, so nothing passes upwards due to a good fit.