Colt Firearms M4 Stripped Upper Features The Colt M4 Stripped Upper is constructed with a black anodized finish providing durability and a sleek appearance. The 16.1 barrel with a 1:7 twist rate ensures superior accuracy and stability for a wide range of ammunition. The muzzle is threaded with a 1/2-28 pattern allowing for the attachment of various muzzle devices to suit your needs. This upper receiver is designed for the AR-15 platform and is perfect for those looking to build or upgrade their rifle. As an assembled upper it includes essential components making it easier to complete your custom build. Colt Firearms M4 Stripped Upper Specifications Manufacturer: Colt Firearms Model: M4 Stripped Upper Cartridge: 5.56 mm NATO Color: Black Finish: Anodized Length: 16.1 Make: AR-15 Muzzle Thread: 1/2-28 Style: Assembled Twist Rate: 1:7