The TA31 RCO is an Advanced Combat Optical Gun sight (ACOG) designed for the M16M4 weapon system (14.5 barrel). It provides the shooter with quick target acquisition at close combat ranges while providing enhanced target identification and hit probability out to 800 meters utilizing the Bullet Drop Compensator. The TA31 RCO incorporates dual-illumination technology using a combination of fiber optics and self-luminous tritium. This allows the aiming point to be always illuminated without the use of batteries. The Tritium illuminates the aiming point in total darkness, and the fiber-optic self-adjusts reticle brightness during daylight according to ambient light conditions. This allows the operator to keep both eyes open while engaging targets and maintaining maximum situational awareness. Designed to the exact specifications of the United States Marine Corps, the unique reticle pattern provides the shooter with quick target acquisition at close combat ranges while providing enhanced target identification and hit probability out to 800 meters utilizing the Bullet Drop Compensator. The TA31RCO-M4CP also includes: 1 Thumbscrew Flattop Adapter 1 4x32 RCO kill FLASH 1 Adjuster Cap Lanyards 1 4x32 Scopecoat 1 Lenspen 1 Trijicon Logo Sticker 1 RCO Manual 1 Warranty Card Technical Specs Magnification 4x Objective Size 32 Bullet Drop Compensator Yes Length (In) 5.8 Weight (oz) 9.9 Illumination Source Fiber Optics & Tritium Reticle Pattern Chevron w/ Target Reference System Day Reticle Color Red Night Reticle Color Red Calibration 0.223 Eye Relief 1.5 Exit Pupil 8 Field of View (Degrees) 7 Field of View @ 100 yards (ft) 36.8 Adjustment @ 100 yards (clicks/in) 2 Mount TA51 Mount Comes With Flattop Housing Material Forged Aluminum ApplicationsLaw Enforcement carbines, rifles, shotguns and submachine guns