Double up on firepower with the ProMag® 9mm 20-Round Polymer Magazine for Glock® 17 Pistols. This aftermarket magazine features proprietary DuPont™ Zytel® based polymer construction with a full-length steel internal insert stamped and welded just like the factory magazine for added strength and durability. A heat-treated chrome silicon wire spring and an injection-molded polymer follower for smooth, reliable feeding in fast-action and tactical environments. If that's not enough, this magazine is backed by a lifetime warranty so you can get years of reliable use. Made in USA.