text: The United States Army and Marine Corps both field the Trijicon TA31RCO ACOG, a 4x magnification model with 32mm optics (4×32), with specially designed ballistic compensating reticles that are fiber optic & tritium illuminated, for the M4 carbine and [M16A4 rifle. This sight is designated the M150 Rifle Combat Optic in Army service and AN/PVQ-31 Rifle Combat Optic in the Marine Corps. After an October 2005 evaluation, the USMC fielded 115,000 ACOGs so that every rifle and every carbine in the Marine Corps inventory would be equipped with one.