GG&G FIRE System rails were designed to mount easily over the integral rails of the M16/AR15 flat top receiver and work in conjunction with our MAD or A2 Style BUIS flip-up rear sights. As they raise the line of sight by 0.5-inch, they offer a proper cheek weld when optical devices are attached. In addition, they serve to protect the flat top receiver's integral rails from the wear associated with quick-release-type mounts. The Scout length rail extends 2 inches beyond the handguards and clears the M4 forearm. It was developed to accommodate long-eye-relief scout-type scopes and also Aimpoint red dot sights with night vision monoculars mounted to their rear.The Standard length rail has been employed mainly as a riser for conventional optical sights. Manufactured from billet 6061 T6 aluminum alloy, black Type III hard-coat anodized, all of the GG&G FIRE System rails meet MIL-STD-1913. These rails lock onto the flat top receiver by means of a locking side bar and round head two socket head screws. This provides both a positive and perfectly aligned lock-up even on well-worn receiver rails. The socket head wrench required for installation is included.