Aim Sports AR5Cub9 Complete Build Kit 5.56X45mm Nato 10.50" Black Nitride Barrel 7075-T6 Aluminum Black Anodized Receiver 10" M-LOK Handguard For AR-15 Mil-Spec Forged 7075-T6 Completely Assembled Upper Rec. Type III Hard Coat anodized For Maximum Durability. M4 Barrel extensions. 10.50" 4150 CMV Steel And Bolt Is 9310 Tool Steel. Both Are Nitride Finish With Excellent Lubricity And Corrosion Resistance properties. Full Auto Profile. Includes Charging Handle And Complete Lower Parts Kit To Build Your AR-Pistol. AR Pistol Buffer Tube, 3.0 Oz Buffer, Carbine Buffer Spring, Castle Nut, And End Plate. LPK Comes With Fire Control Group And A2 Grip. Type: Complete Caliber: 5.56X45mm Nato Sights: None, Optic Ready Barrel Length: 10.50" Barrel Material: 4150 Chrome Moly Vanadium Steel Twist: 1:8" Barrel Finish: Black Nitride Receiver Finish: Black Hard Coat Anodized Handguards: 10" M-LOK Handguard Finish: Black Hard Coat Anodized Barrel Length Range: 10" To 10.99"