The XTech Tactical Magazine Extension is compatible with factory magazines and installs in seconds. Unlike other shield mag extensions on the market, the Patented design permits for a consistent internal wall throughout the extender, which is smaller than the M&P magazine tube. The included spring was engineered specifically for the M&P Shield 9mm to allow for unmatched reliability and last round slide hold open. For use with the .40 S&W the extender uses the factory spring. XTech Tactical's MTX line of extenders are simply unmatched for reliability, ease of installation, and durability! FeaturesFits M&P Shield 9mm and 9mm 2.0.For use with .40 S&W 1.0 and 2.0 use factory springNot compatible with Shield 9mm EZMP Shield mag extension adds 2 rounds to both the factory 7 and 8rd magazinesUses factory sleeve when used with the 8rd magazineTool free, easy installationCustom engineered springOptimal ergonomics and texture for recoil controlUses factory follower & body (Not Included)Adds 1...