MK18 Rail Interface System II, RIS II Daniel Defense is the Sole Source Provider of the RIS II to the United States Special Operations Command! The Daniel Defense MK18 RIS II is designed to work specifically on the MK18 CQBR! The Daniel Defense Rail Interface System (RIS II) was designed at the request of the United States Special Operations Command (SOCOM) for the SOPMOD II program. The RIS II MK18 is NOT compatible with an M203. Details The Daniel Defense RIS II is to be used in conjunction with the MK12 Low Profile Gas Block. The Daniel Defense RIS II free-floating Picatinny rail systems are designed to allow individual operator to quickly and precisely mount SOPMOD accessories to host weapon without effecting point of impact. The Daniel Defense RIS II is an innovative upgrade to the M4 platform. Features Free Floating Barrel Design Uninterrupted Upper Rail Platform Aircraft Grade Aluminum Hardened Steel Barrel Nut Grade 8 Military Specification Fasteners Mil-Spec 1913 Picatinny Rails Materials & Construction Precision CNC machined from Aircraft Grade Aluminum and Military Specification Type II Hard Coat Anodized in SOCOM approved Flat Dark Earth. Material: Aircraft Grade 6061-T6 Aluminum Finish: Military Specification Flat Dark Earth Anodizing Length: 9.55" Width: 2.23" Weight 14.1 Ounces Inside Diameter: 1.15" Made in the USA!