The TA31USN-M855 is an Advanced Combat Optical Gunsight (ACOG) designed for either the M16A4 weapon system (20” barrel) or the M16M4 (14.5” barrel). It incorporates dual illumination technology using a combination of fiber optics and self-luminous tritium. This allows the aiming point to always be 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. - The unique reticle pattern provides quick target acquisition at close combat ranges while providing enhanced target identification and hit probability out to 1000 meters utilizing the Bullet Drop Compensator. - No tools are needed for windage and elevation adjustments because the TA31USN-M855 features external adjusters making it waterproof up to 11m without the caps. - The TA31RCO-M855 includes: - 1 LaRue Tactical Mount (LT799) - 2 Assemblies 1/10 Miliradian External Adjusters - 2 External Adjuster Caps - 1 Lanyard Assembly for Adjuster Caps (TA71E) - 1 Scopecoat (TA96) - 1 LENSPEN® (TA56) - 1 RCO Manual - 1 Warranty Card - Magnification : 4x - Objective Size (mm): 32 - Bullet Drop Compensator: Yes - Length (in): 6.0 - Weight (oz): 14.2 - Illumination Source: Fiber Optics & Tritium - Reticle Pattern: Horseshoe w/Dot w/ Target Reference System - Day Reticle Color: Red - Night Reticle Color: Red - Calibration: 0.223 (14.5 or 20 in. barrel) - Bindon Aiming Concept: Yes - Eye Relief (in): 1.5 - Exit Pupil (mm): 8 - Field of View (Degrees): 7 - Field of View @ 100 yards (ft): 36.8 - Adjustment @ 100 yards (clicks/in): 2 - Mount Comes With: LT799 - Housing Material: Forged Aluminum