The SR-556 offers Ruger's legendary rugged reliability and comes factory standard with a host of accessories that today's shooters demand. The SR-556 employs a patent-pending, chrome-plated, two-stage piston driven operating system that provides the user with a cleaner, cooler running, reliable firearm that is truly state-of-the-art. Its tool-less takedown barrel is removed from the upper receiver by simply moving the slider bar towards the breech and rotating the barrel to pull it free. Ruger Elite 452 two-stage AR-Trigger offers a smooth, crisp, 4.5 pound trigger pull. The full-strength hammer spring offers consistent primer ignition and the lightweight hammer provides a 30% faster lock time over standard MSR triggers. Front and rear folding iron sights; front sight is elevation- and windage-adjustable. Magpul MOE grip on lower receiver. Magpul MOE SL collapsible buttstock on the mil-spec buffer tube. Slim, lightweight KeyMod handguard for reduced overall weight. Threaded barrel fitted with Ruger flash suppressor. Includes a carrying case, lock, and three 30-round Magpul PMAG magazines.