All StormLake barrels are machined from solid firearms grade 416 stainless steel bar stock and hardened to 40-42 HRC. Rifling features one turn per 16 inches with a left hand twist. StormLake is dedicated to excellence in accuracy" excellence in quality" and excellence in value. This is our guarantee. All StormLake barrels are proudly made in the USA. Specifications Finish Stainless Material Stainless Steel Barrel Length 4.25 Inches Twist 1:16 Threaded Muzzle No Country of Origin United States of America Compatible With Smith & Wesson M&P Pistol Auto