Noveske Barrel Nut NSR/NHR 3rd Gen N4 Manganese Phosphate. This part is reversible for precise timing on 3rd generation models. Specifications for Noveske Barrel Nut NSR/NHR 3rd Gen N4 Manganese Phosphate: Manufacturer: Noveske Color: Black Gun Model: AR-15 Fabric/Material: Steel Finish: Manganese Phosphate Black Handle Color: Black Features of Noveske Barrel Nut NSR/NHR 3rd Gen N4 Manganese Phosphate: 1 1/16 Wrench Flats Included" Package Contents: Noveske Barrel Nut NSR/NHR 3rd Gen N4 Manganese Phosphate What firearm models does the manufacturer say Noveske Barrel Nut NSR/NHR 3rd Gen N4 Manganese Phosphate is compatible with? The manufacturer says that Noveske Barrel Nut NSR/NHR 3rd Gen N4 Manganese Phosphate is compatible with AR-15