This KAC M4 R.A.S. switches from the common hand guards on fourteen.5 & sixteen inch MILSPEC carbine barrels. Applied as being a drop in quad rail for the AR15 System. Picatinny rails on all sides enable a number of choices for all your mounting options. Extras mount immediately and easily. https://knights-armament-drop-in40510.blog5.net/65235439/not-known-facts-about-knights-armament-drop-in-rail