[b]Advanced Combat Optical Gunsights[/b] (abbreviated [b]ACOG[/b]) are a series of telescopic sights manufactured by "Trijicon":http://www.trijicon.com/. The ACOG was originally designed to be used on the [[m16|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.