The Foxtrot Mike Products FM-15 Gen 2 Side Charging AR-15 Upper Receiver features a unique dual spring recoil system nested in the top of the upper receiver allowing the use of a folding stock. This recoil system is paired with a pistol-length direct impingement gas system and a proprietary lightweight bolt carrier group for a smooth and reliably functioning rifle.Features: Machined from a billet of aluminum. 2 Position side charging handle (Left or Right) Slim M-LOK handguard .223 Wylde chambering Proprietary lightweight BCG Picatinny rail adapter with QD sling mount 9" barrel Pistol gas system Compatible with Mil-Spec lowers (buffer and buffer spring will not be used)The barrel features a .223 Wylde chamber and a 1:8 twist rate for compatibility with a wide range of ammunition. Additionally, it features a lightweight contour and at 9 inches in length.