Styrka S3 Series 2.5MOA Red Dot Sight, Black (ST-73050) Double lens optical system enhances optical quality while virtually eliminating parallax Optical coatings are indexed to specifically match the wavelength of the red or green dot, virtually eliminating parallax and point-of-aim errors Six brightness settings allow the intensity to be set to the surrounding conditions True 1x design with unlimited eye Relief for quick and easy target acquisition Waterproof and nitrogen purged to prevent internal fogging