The ACOG is internally-adjustable, compact telescopic sights with Tritium-illuminated reticle patterns for use in low light or at night. It combines traditional, precise distance marksmanship with close-in aiming speed. This model is designed for use with the M16 family, every feature of its mechanical and optical design was chosen for a single purpose: to provide increased hit potential in all lighting conditions, without failure prone batteries.ACOG 5.5x50 red Chevron BAC flattop .308 reticle includes flat top adapter. The chevron reticle is designed to be zeroed using the tip at 100m. The width of the chevron at the base is 5.53 MOA which is 19 inches at 300 m. This allows range estimation for silhouette targets. Features: Always on, always ready - most ACOG models are battery free, featuring a tritium/fiber optic illuminated reticle that automatically adjusts the brightness based on available light "Both eyes open" design - shooting using the Bindon Aiming Concept (BAC) allows for improved situational awareness Combat proven - no other magnified optic has been used more in combat than the ACOG Take control - several ACOG models are designed with a user adjustable brightness setting powered by a single AA battery, the 3.5x35 LED and 4x32 LED models both offer six adjustable brightness settings Outstanding clarity - the quality of the glass and multi-coated lenses maximize light-gathering capabilities and clear field of view with zero distortion Shock-resistant - proven to withstand recoil from a .22 LR to a .50 BMG and everything in between, easily passes US Military drop test requirements Rugged, reliable housing design - fixed-power design allows for minimal moving parts to create a nearly indestructible sighting system Exact target distances and holds - most ACOG models feature a bullet drop compensating and target-ranging reticle for decisive aiming Waterproof - exceptional waterproof performance that exceeds military standards, dry nitrogen-filled to eliminate fogging Fiber optics and tritium power and illumination source