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 carbine length direct impingement gas system and a proprietary lightweight bolt carrier group for a smooth and reliably functioning rifle. The 3 position adjustable gas block features an indexing pin and a coil pin to keep it locked in place against the lightweight contoured barrel for an extremely robust system.Features:Machined from a billet of aluminum4 Position side charging handleSlim M-LOK handguard.223 Wylde chamberingProprietary lightweight BCGPicatinny rail adapter with QD sling mount9" barrel3 Position adjustable gas block Carbine gas systemCompatible with Mil-Spec lowers (buffer and buffer spring will not be used)Specifications:Barrel Length9Brand Foxtrot Mike ProductsCaliber Gauge.223 WyldeColor BlackFinish Hardcoat AnodizedGas System Length CarbineHandguardMuzzle Device FM Blast DiffuserTwist Rate1:8