WHAT DOES KNIGHTS ARMAMENT M4 QUAD RAIL MEAN?

two rail. I have shot 18s with rifle fuel like how clean and correct These are. I'm able to set more money into efficiency pieces then clone appropriate parts just like a ops brake and collar that I don't have a can for.just one facts issue, I picked up a handful of salty employed P&S M4 RAS's from Thoroughbred for $one hundred fifty ea. yeah, not