It doesnt seem to move enough air. I wear glasses so moving air is essential! Also, there is only 1 small fan, and its on the right side, so you only get your right eye back when it actually does something.
I installed 2 computer fans up there, and glued a switch and put a 9 volt under the elastic strap, wired it all up (made it all waterproof) and it moves air like a dream, fog is nonexistant now!
Its alright, if you dont wear glasses, just get a thermal lens, if you do wear glasses, it will help a bit... but its not worth the money