This item is the Scout Length Mounting Rail
These two GG&G optical mounting rails were designed to mount easily over the integral rails of the AR15/M16 flat top receiver and work in conjunction with any of our back up iron sights. As they raise the line of sight by 1/2 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 damaging wear associated with lever type quick-release mounts, especially those without buffer pads.
The Scout length rail extends two 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.
Both are manufactured from billet 6061 T6 aluminum alloy, black Type III hard-coat anodized per Mil-Spec, and meet MIL-STD-1913. These rails lock onto the flat top receiver by means of a full locking side bar and two round head 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.