I've been using one of these for a few years now. I find that it makes winter riding more comfortable by minimising draughts and flow of cold air around the bottom of my helmet, but it doesn't cut out much wind noise (for me). I still get some whistling from below my ears, where the skirt does not seal fully against my neck. I think I need a bigger neck, or a different shape head. Simple to fit to any full face helmet.
