The One Horse M4 Nitride Barrel is precision-engineered for AR-15 platform rifles featuring a durable nitride coating and chambered in 5.56 NATO with a 16-inch length.One Horse M4 Nitride Barrel (SKU: OH-BR01)5.56 NATO chamber specification16-inch barrel lengthMid-length gas system for optimal cyclingNitride coating for enhanced durability and corrosion resistanceDimensions: 1.35 X 4.05 X 17.55 inches (packaged)Ideal for building or upgrading AR-15 rifles this barrel combines reliable performance with long-lasting protection through its advanced nitride finish treatment.