Trijicon TA31-ECOS ACOG 4x32 Flat Dark Earth Scope, Dual Illumination Crosshair Reticle with 3.25 MOA RMR Sight BATTERY-FREE ILLUMINATION: Features a tritium / fiber optic illuminated reticle that automatically adjusts the brightness based on available light "RUGGED ALUMINUM-ALLOY HOUSING: Forged 7075-T6 aircraft-aluminum-alloy housing provides for a nearly indestructible sighting system" BULLET DROP COMPENSATING & RANGING RETICLE: The ranging reticle is calibrated for 5.56(.223 cal) flattop rifles out to 1,000 meters BOTH EYES OPEN DESIGN: The ACOG can be used as a CQB sight when shooting both eyes open utilizing the Bindon Aiming Concept SUPERIOR QUALITY GLASS LENSES: Multi-coated lenses provide superior clarity and light gathering capabilities with zero distortion