Caliber: 5.56 NATO. Faithful reproduction of the first-ever AR-15 issued to the U.S. Military during the early 1960s. Based on iconic Model 601 rifle, which entered military service with the U.S. Air Force and other military units in SE Asia during the early years of the 1960s. The rifle is constructed from all-new parts and features green furniture and slab-side receivers that are close to the original design envisioned by Eugene Stoner. Triangle-shaped charging handle, three-prong flash hider, and a slick-side bolt-carrier group. Length: 40 in. Weight: 6.7 lbs. As of 2022, only available as a build kit, not as a complete rifle.