This replacement magazine for the Smith & Wesson Shield chambered in .40 caliber is constructed from heat-treated blued-steel. Its components molded from our proprietary Technapolymer and the anti-fatigue spring, so you can keep the magazine loaded and ready for up to six years without concern. ProMag magazines are designed utilizing traditional stamping and welding of heat-treated high carbon steel. Every ProMag magazine is backed by a lifetime guarantee against manufacturer's defects.Features:Magazine body constructed of heat treated carbon steel with black oxide finishInjection molded magazine followerMagazine spring formed from heat treated chrome silicone wireMade in USASpecifications:Type: ExtendedCapacity: 9Caliber: 40 S&WFits Model: Smith & Wesson Shield PistolMaterial: Carbon SteelFinish: Blue