The KAC UK-SAS M4 RAS Bottom Rail Assembly was designed at the request of a foreign military unit as a replacement for the standard M4 RIS or M4 RAS bottom rail. Unlike a standard RIS or RAS lower rail that relies upon the delta ring assembly and handguard end cap to keep it in place, the UK-SAS Bottom Rail locks onto the barrel nut via a clamp and screw arrangement, making for a much more solid and secure system. Includes a heat shield.

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