The KAK 4 Prong Flash Hider is heat Treated for strength and durability. Phosphate Coating offer superior corrosion resistance. Milled wrench flats so no special tool needed for installation. Crush washer not included. This extended flash hider will extend a 13.9" barrel to legal non-NFA length when pin and welded. FeaturesCNC machined from bar steelHeat treated for strengthPhosphate coated to protect from corrosionAdds approximately 2.125" to overall length of barrel when pinned and welded..125" hole pre-drilled for pin and weld