The Trijicon ACOG (Advanced Combat Optical Gunsight) optical sight is by far one of the most respected optics available today. The Trijicon ACOG is built from the ground up to be able to stand up to the rigors of extreme combat and duty use in any environment. No wonder that when their US Special Forces go out on mission chances are there is an Trijicon ACOG mounted on their firearm. Don’t accept knock offs or inferior products when your life is on the line go with the very best, go with a Trijicon ACOG.