This M4 carbine-length, drop-in quad rail by Aim Sports is an easy to install upgrade for the basic carbine. Made from aircraft-grade aluminum, it is compatible with most carbine-length direct impingement gas systems. The two-piece design requires no gunsmithing to install and is compatible with all standard Weaver/Picatinny 1913 accessories. It is 6.5" long and weighs 11.03 oz. This model has a black anodized finish.The M4 carbine length drop-in quad rail is an easy to install upgrade for the basic carbine. Made of black anodized aircraft grade aluminum and compatible with most direct impingement gas systems. When installing the 2-piece design no gunsmithing is required. Features: Accepts all standard Weaver/Picatinny 1913 accessories Compatible with most carbine length direct impingement gas systems No gunsmithing required