Daniel Defense's Rail Interface System or RIS II was originally designed at the request of the United States Special Operations Command (SOCOM) for SOPMOD II program. This program had a specific requirement to free float an M203 grenade launcher without additional parts, and Daniel Defense delivered. The RIS II itself features four picatinny rails in the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions with plenty of space to mount accessories such as tactical lights/lasers, fore-grips, iron sights, and optics. The RIS II utilizes Grade 8 Mili-Spec fasteners, and a battle-tested 6-bolt system to attach to the handguard of the upper receiver. Features: Free-Floating barrel designTwo-Piece Design for USSOCOM Allows For the Attachment of an M203 Grenade Launcher When Lower Rail Section is Removed. Battle-Tested, 6-Bolt Bolt-Up System Securely Attaches Handguard to the Upper ReceiverGrade 8 Military Specification FastenersUninterrupted Upper Rail Platform & Mil-Spec 1913 Picatinny RailsMil-Spec Type III Hard Coat Anodized Finish (FDE or Black) Daniel Defense RIS II M4A1 FSP FDE Rail Interface System Assembly 01-004-08030