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 finish Injection molded magazine follower Magazine spring formed from heat treated chrome silicone wire Made in USA #html-body [data-pb-style="62DF828865F42"]{justify-content: flex-start; display: flex; flex-direction: column; background-position: left top; background-size: cover; background-repeat: no-repeat; background-attachment: scroll; border-style: none; border-width: 1px; border-radius: 0px; margin: 0px 0px 10px; padding: 10px;}#html-body [data-pb-style="62DF828865F4F"]{border-style: none; border-width: 1px; border-radius: 0px; margin: 0px; padding: 0px;}