AIM Sports Inc Complete AR Rifle Kit Mid-Length 300 Blk 16in Black Large Black Large. Specifications for AIM Sports Inc Complete AR-15 .300 Blk 16in Upper Receiver W/ BCG LPK & Mil Spec Stock Buffer Kit: Manufacturer: AIM Sports Inc Caliber: .300 AAC Blackout Barrel Length: 16 in Color: Black Features of AIM Sports Inc Complete AR-15 .300 Blk 16in Upper Receiver W/ BCG LPK & Mil Spec Stock Buffer Kit 16" Barrel 4150 Chrome Moly Vanadium Steel A2 muzzle brake and crush washer Mid length gas tube and low profile gas block Mil-Spec Forged 7075-T6 complete Upper with dust cover and forward assist Bolt Carrier Group 8620 steel and bolt is 9310 tool steel with a Nitride finish Mil Spec Buffer Kit - 3.0oz buffer carbine spring castle nut end plate mil-spec buffer and stock Lower Parts Kit - Complete lower parts kit includes fire control group and A2 Grip Package Contents: AIM Sports Inc Complete AR-15 .300 Blk 16in Upper Receiver W/ BCG LPK & Mil Spec Stock Buffer Kit AIM Sports Inc AR5CUB11: Complete AR Rifle Kit Mid-Length 300 Blk 16in Black Large AR5CUB11 Black Large