Daniel Defense 00408030: 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. It allows the individual operator to free-float the M203 grenade launcher without additional parts. The Daniel Defense RIS II M4A1 FSP features a cut out in the top rail to accommodate a standard front sight base on a carbine length gas system.