The M4A1 AR15 style Upper Receiver Group is built around a 14.5 inch Cold Hammer Forged M4 Profile barrel with a permanently attached Daniel Defense Flash Suppressor, a GRIP-N-RIP Charging Handle, and our mid-length gas system. It features a 12.5 inch lightweight RIS III rail-modeled after the revolutionary RIS II two-piece handguard developed for SOCOM-features M-LOK attachment for lighter weight. All Daniel Defense complete upper receiver groups come standard with an M16 profile bolt carrier group.