Parallax-free aiming with a single, bright glowing red dot; proven to be the fastest, most accurate sighting system available. Exclusive Advanced Circuit Efficiency Technology (ACET) greatly improves the useable life of the single 3-volt battery. ACET sights can last nearly 50,000 hours (over five years on setting 7 out of 10) of constant use. AA battery model can last up to 80,000 hours with a single battery. All sight housings are machined, or extruded from 6000 series aluminum for maximum strength. Lens surfaces are optically ground (not cast) for superior clarity. Proprietary housing and lens sealing material keeps electronic and lens surfaces dry, fog-free and fully functional regard Mfg: Aimpoint