This M4-Contour AR-15 Barrel is fully chambered and ready for installation onto a host upper receiver. The barrel features a true 5.56x45mm NATO Chamber. The barrel's M4 Contour sheds excess weight and bulk, and comes complete with the military standard M203 cut. This barrel is an excellent choice for a general purpose AR rifle build that's perfectly suited for use at the range, in a 3-Gun match, or in the field pursuing game. Barrel nut, handguard cap, fixed front sight base assembly, barrel extension, and locator pin are included and factory installed. The FSB is installed after the barrel is coated.