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. SOCOM had a specific requirement for a free float M203 solution and Daniel Defense responded" designing a revolutionary product to meet the government's need. The Daniel Defense RIS II allows the individual operator to free float the M203 grenade launcher without additional parts. Additional features include: Aircraft Grade 6061-T6 Aluminum construction" Free-Floating Barrel Design For Increased Accuracy" Battle-Tested" 6-Bolt Bolt-Up System Securely Attaches Handguard to the Upper Receiver" Grade 8 Military Specification Fasteners" Uninterrupted Upper Rail Platform & Mil-Spec 1913 Picatinny Rails and Mil-Spec Type III Hard Coat Anodized Finish. Dimensions: Length - 9.55" " Width - 2.23" " Height - 2.25" " Weight - 14.1 " Inside Diameter - 1.15"