The MK111 MOD 2-M Upper operates on the highly acclaimed PWS Long Stroke Piston System, renowned for its reliability and reduced fouling. The inclusion of a 3-setting Adjustable Gas System allows users to fine-tune gas flow, ensuring optimal performance in diverse shooting conditions as well as optimizing it for suppressor use.Key FeaturesBarrel Length: Features an 11.85-inch barrel for compact versatility.Caliber: Chambered in .223 Wylde for compatibility with both .223 Remington and 5.56 NATO cartridges.Barrel Finish: Finished in black for a sleek appearance.Sights: Optic ready for easy mounting of your preferred sighting system.Rate of Twist: 1-8 twist rate for optimal stabilization of a wide range of bullet weights.