Geissele 08-543B Super Duty MOD1 5.56 NATO 10.3" 1:7" CHF Chrome Lined Bbl Black Complete Upper Receiver GroupThe Geissele Super Duty MOD1 5.56 NATO 10.3" Complete Upper Receiver Group 08-543B features a 10.3-inch barrel with a 1:7" twist rate, cold hammer forged (CHF), and chrome-lined for durability and reliability. This Geissele 08-543B complete upper receiver group comes in black and is designed to provide top-notch performance for AR builds..yellow-box p {font-size:16px}.special-tab {color: #FFFFFF}.yellow-box ul li {font-size: 16px;}The Geissele Super Duty MOD1 Complete Upper Receiver offers top-tier components for a custom AR build. Geissele Super Duty MOD1 Upper Receiver is precision-machined, cold hammer forged barrel is made from high-quality steel, coated with manganese phosphate and chrome lining for durability against the elements. The HUXWRX Flash Hider-QD 556 muzzle device enhances performance and is suppressor-ready. The included Reliability Enhanced Bolt Carrier Group features Nanoweapon coating, properly staked gas key, and a cam pin machined from H13 tool steel for corrosion and wear resistance. Extended upper rails improve stability and feeding reliability, while the Stressproof Bolt offers superior strength and fatigue resistance. The updated MK16 Super Modular Rail ensures a secure fit for a variety of optics, including iron sights, red dots, scopes, and thermal/night vision devices. Features of the Geissele Super Duty MOD1 Upper ReceiverPrecision machined, cold hammer forged barrelHUXWRX Flash Hider-QD 556 muzzle deviceGeissele own Reliability Enhanced Bolt Carrier GroupGeissele Stressproof BoltAirborne Charging HandleUpdated MK16 Super Modular Geissele Super Duty MOD1 5.56 NATO 10.3" 1:7" CHF Chrome Lined Bbl Black Complete Upper Receiver Group 08-543B