Advanced Combat Optical Gunsights (abbreviated ACOG) are a series of telescopic sights manufactured by Trijicon. The ACOG was originally designed to be used on the M16 rifle and M4 carbine, but Trijicon have also developed ACOG accessories for other firearms. Models provide fixed power magnification levels from 1.5× to 6× ACOG reticles are illuminated at night by an internal phosphor. Some versions have an additional daytime reticle illumination via a passive external fiber optic light pipe.
