Two rail. I've shot 18s with rifle fuel like how clean and correct they are. I'm able to set extra money into overall performance components then clone proper sections just like a ops brake and collar that I don't have a can for. Large Ability matches replicate the USMC Table https://m4-ras-handguard64062.webbuzzfeed.com/30047842/5-essential-elements-for-knights-armament-quad-rail