The Lancer Tactical Emerson SI Helmet Mounted Goggles are designed specifically for use with helmets that provide the necessary Arc rail space to mount the goggle straps onto for easy carrying and use. Using the helmet as a mounting surface instead of a strap around the user's head allows for a more comfortable and adjustable fit. It also allows for the wearer to keep their head set up as one piece. Featuring interchangeable lenses, these goggles can be made to have clear or smoke lenses with the included lens options. So whether in low light or in full daylight these will be able to keep your vision clear.