The Full-Size M&P9A(R) and M&P9 2.0A(R) +5 Magazine Extender is compatible with factory magazines and installs in seconds. Unlike other extenders on the market, The Patented design of the MTXA(R) permits for a consistent internal wall throughout the extender, which is smaller than the magazine tube. The included spring was engineered specifically for the M&P9A(R) line to allow for unmatched reliability and last round slide hold open. XTechA(R) Tactical's MTXA(R) line of extenders are simply unmatched for reliability, ease of installation, and durability!" Mfg: Xtech Tactical