This is a ProMag® .40 S&W STEEL 15-round extended magazine for Sig® Pro pistols.
Combining heat-treated steel construction with ProMag’s proprietary anti-fatigue springs and ultra-rugged Zytel™ polymer baseplates & followers, these magazines deliver impressive performance at a price that’s hard to beat. Sig Sauer® PRO handguns have long been on the cutting edge of polymer pistol innovation. Like all ProMag magazines, they come with a lifetime replacement guarantee—so you’ll always have a working magazine on hand, no matter what.