Trijicon RS20 AccuPower 3-9x40 Riflescope Superior Quality Lenses: Multi-coated lenses provide superior clarity and light gathering capabilities with zero distortion Illuminated Reticle: Powered by a CR2032 battery Adjustable Brightness Settings: Eleven brightness settings with an Off feature between each brightness setting Aircraft-Grade Aluminum Housing: All-weather rugged construction protects against the toughest elements Second Focal Plane Reticle: Reticle size remains constant as magnification increases which provides a more exact aiming point at higher magnifications