Perfect for anyone looking to extend their firearms magazine capacity this drum mag from ProMag holds 50 rounds and is compatible with the Sig Sauer MPX.The body is constructed of a proprietary DuPont Zytel-based polymer and has a heat-treated stamped steel upper magazine housing.In addition it includes an injection-molded magazine follower and a heat-treated stainless steel wire.ProMag Sig MPX 9mm Drum Magazine50 Round CapacityFits Sig Sauer MPX 9mmOrder your ProMag Sig MPX 50-round drum magazine online today!Score big savings and fast shipping when you shop our large selection of 9mm ammo in bulk available online at Ammunition Depot.Score big savings and fast shipping on all your favorite rifle and pistol ProMag Magazines available online at Ammunition Depot.