What sets the M4 RAS other than other 2-piece quad rails out there is it securely locks on the rifle’s barrel nut by means of a clamp and screw arrangement, which makes it an extremely strong foundation upon which to mount tactical extras. Involves 3 KAC 11 Rib Rail Panels. https://knights-armament-rail30628.thekatyblog.com/26177222/the-definitive-guide-to-kac-m4-ras