Fast Loading Magazine Changer for AR15, M16 and M4. Now you can change magazines fast and easy on your AR15/M16 and M4 rifles with the Redi-Mag magazine system. This clip holder fits onto the receiver without modification to the rifle. Your extra magazine is right there - at your fingertips when you need it. Eliminates the need for extra cartridge carriers, belts or "jungle rigging" to carry extra ammo. Close the action fast on that fresh clip with just a quick push of the bolt catch release button. This feature also enables the user to quickly lock open the bolt in the event of a weapon malfunction.