LWRC's IC-PSD Upper Receiver is perfect for a custom AR SBR or AR Pistol build. It comes equipped with a patented LWRCI short-stroke gas piston system, a system renowned for its dependability and ease of maintenance. The Upper also comes standard with a nickel-boron coated bolt carrier for unmatched resistance to wear and corrosion while also providing permanent lubricity. Additionally, the IC-PSD features a modular rail system with individual rail sections allow the shooter to place accessory rails where they are needed while maintaining its low profile ergonomic fit and function. Features: Proprietary Short Stroke Gas Piston SystemOne Piece Gas Block User Configurable Rail System Ambidextrous Charging Handle LWRC International LWRC IC-PSD 5.56mm NATO 8.5" 1:7" 1/2x28 Bbl Patriot Brown Personal Security Detail Complete Upper Receiver ICPSDU5PBC8