Featuring a 1/2x28 threaded muzzle with a knurled thread protector, the Lone Wolf Arms AlphaWolf 1/2x28 Threaded 9mm Conversion Barrel for Gen 1-4 Glock® 27 / 33 Pistols is a drop-in caliber conversion. Crafted of stress-relieved and heat-treated 416 stainless steel construction, finished with a corrosion-resistant SBN (Salt Bath Nitride) coating for a surface hardness of RC 60. The button-rifled, three-stage honed bore delivers match-grade accuracy, and the proprietary fluting pattern reduces weight and facilitates faster cooling. Machined to exact tolerances for drop-in installation and safe and consistent performance. Made in USA.