I've got one in my Shoei Steve, it's amazing. No fog at all. Had a horrible time with it in wakey last winter when it wasn't adjusted correctly. If you don't have them tightened properly, they become a nightmare as your visor ends up fogging between the two layers and not even cracking it open clears it. Get it right and they just work. I have no idea if it's the same for all brands of helmet though? Just my experience with the Shoei one.