Our GS-1 FIRE System rail was designed for mounting a conventional-type scope on the M16/AR15. It provides significantly longer eye relief for a proper scope/operator interface and the capability of attaching additional optical devices, such as a night vision monocular. The back of the rail has been tapered to blend with the rear of the upper receiver and is not designed to mount a BUIS flip-up rear sight. It extends 3 inches over the handguards and clears the M4 forearm. Manufactured from 6061 T6 aluminum alloy, black hard-coat anodized, the GS-1 rail meets MIL-STD-1913. As with the other FIRE System rails, it locks onto the flat top receiver by means of a locking side bar and two socket head screws. It’s available, on request, with 20 MOA of elevation built in.