The KAC M5 RAS (Rail Adapter System) was developed for use on the US militarys M16A4 and with hundreds of thousands of rails issued to date, it is one of the most battle proven designs available for the AR-15 platform. This non-free float handguard is a simple-to-install, drop-in upgrade that features genuine Mil-Spec M1913 Picatinny Rails along its entire length. What sets the M5 RAS apart from other 2-piece quad rails on the market is that it securely locks to the rifles barrel nut via a clamp and screw arrangement, making it a very solid foundation upon which to mount tactical accessories. Includes three KAC 11 Rib Rail Panels. Rifle Requirements- The M5 RAS is a drop-in replacement part for standard, 2-piece polymer, A2-type handguards. The rifle must have a rifle length gas system, delta ring assembly, fixed front sight/gas block, and either a round or triangular handguard end cap. Lighter barrel profiles work best (Government contours). Heavier barrel contours may require modification to the inside of the rail. *For AR-15/SR-15 based platforms only; not compatible with SR-25 variants. Installation instructions are included.