Aimpoint CompM2

The CompM2 is a battery-powered, non-magnifying red dot type of reflex sight for firearms manufactured by Aimpoint AB. It was first introduced in the U.S. Armed Forces in 2000 , designated as the "M68 Close Combat Optic" (M68 CCO; NSN: 1240-01-411-1265). It is also known as the "M68 Aimpoint" and is designed to meet United States military standards. The sight is designed for use with the M16/M4 family of rifles, but can be mounted on any weapon fitted with an upper Picatinny rail. It is also NVG-compatible—the aiming dot is still visible through night vision scopes and goggles.
Overview.
The sight is water-tight down to 25 meters and runs on one 3-volt lithium battery type 2L76 or DL1/3N. Aiming dot brightness is adjustable for better visibility or increased battery life.
The M68 is parallax-free at around 45.7 m (50 yards), meaning that the red dot will not change position based on eye position at that range. At shorter ranges the point of aim will change position based on eye position with the maximum error being equal to the radius of the sight's optical window at short range.
The CompM2 is used across branches of the U.S. Armed Forces, Sweden, and various NATO countries, among them Norway. A variant known as the ECOS-N (NSN: 1240-01-495-1385) is also issued as part of the U.S. SOPMOD kit. The sight is also available on the civilian market and is employed by various law enforcement organizations (especially for SWAT type situations that involve close quarters work) and by recreational shooters.
By August 2011, the U.S. Army had bought 1,000,000 M68 Close Combat Optics. Some 85 percent of Army M4s are issued with the CCO, though optics can vary depending on unit. The sight allows soldiers to engage targets out to 300 meters while keeping both eyes open for situational awareness. Post combat surveys show an 85 percent acceptance rate of the CCO as an effective optic and for its value for close quarters fighting.