The tacfire ss-rk556 rifle build kit contains- 16" 5.56 nato m4 contour barrel/nitride; birdcage flash hider w/crush washer; 15" mlok free float handguard; ar15 5.56/.223/.300 aac stripped billet upper receiver w/m4 feed ramps/.556 mil-spec charging handle aluminum w/steel latch; dust cover; ar-15 forward assist; ar-15 standard receiver end plate; mil-spec/commercial castle nut/steel; buffer tube aluminum; ar 15 3 oz buffer w/tube spring; ar-15 usa made lower parts kit and a ar-15 standard a2 style black pistol grip/a2 style.*sports south exclusive.Finish: Black NitrideModel: Lower Parts KitMaterial: AluminumAction: Semi-AutoTrigger: Mil-SpecThread Pattern: 1/2"-28 tpi