Buy Mossberg 500 Tactical Flex 12 Gauge Pump Action Shotgun. The Mossberg FLEX TLS (Tool-less Locking System) is a series of three patent-pending connectors that allow shooters a simple method of switching stocks, forends, and recoil pads for a variety of shooting applications. FLEX base model shotguns, when used with interchangeable FLEX Stock, Forend and Recoil Pad Accessories can create virtually limitless combinations of fit, style or application. All this while still maintaining the same great features that made the Mossberg 500 legendary- ambidextrous safety, dual extractors, positive steel-to-steel lockup, twin action bars, and smooth operating anti-jam elevator.