If you're building a bench gun, a tack-driver that runs smooth like a Cadillac, this is your upper. As with our other NBS complete uppers, we've carefully chosen proven components from reputable suppliers. At it's core this unit features a 18" 416R Stainless Barrel chambered in .223 Wylde with a 1:8 twist paired with NBS's Beautiful Nickel Boron BCG. When it comes to any weapon the little things matter. And true to our promise of never cutting corners, we always dimple our barrels, use a quality nitrided steel gas block and stainless steel gas tube. For this particular upper we chose a M-LOK handguard and finished it off with a Competition Muzzle Brake to keep muzzle rise and felt recoil to an absolute minimum. This isn't a cheap upper that you'll buy and end up replacing every component before you're happy with it. Each part can already be considered an upgrade over what many budget uppers use.AMERICA Made - Lifetime WarrantyUpper Receiver- 7075-T6 aluminum- M4 Feedramps- .250 takedown pin holesBarrel18" .223 Wylde 1:8 Twist- Shoots both .223 and 5.56- Mid-Length Gas System- Heavy Barrel- 416R Stainless Steel- Spiral FlutedBolt & Carrier GroupNBS Nickel Boron M16 Bolt Carrier Group .223/5.56- Full Auto Capable- 9310 MPI and HPT Tested Bolt- Case Hardened 8620 Carrier- 4130 Gas Key- Grade 8 Hardware With Proper Staking- Gas Key Sealed With Permatex No.3- 8740 Hard Chrome Firing PinCharging HandleStrike Industries Extended Latch Charging HandleGas SystemMid-Length- APOC Armory Black Nitride Steel Lo-Pro Gas Block- Stainless Steel Gas TubeHandguardMay Vary from batch to batch Muzzle DeviceBlack Nitride Competition Muzzle Brake