AR15 Carbine/M4 Quad Rail Handguard replaces factory 6.5" AR15 Carbine/M4 handguards. The Quad Rails allow the attachments of lights, lasers, vertical grips, and other accessories that can mount onto weaver/Picatinny/ MIL STD 1913 type rails. NcSTAR's 3rd Generation MAR4S, AR15/M4 Carbine Length Quad Rail Handguard. The 3rd Gen MAR4S is now lighter and has a slimmer profile than earlier models. Fits onto AR15 Carbines/M4 with the carbine length gas system using the GI Handguard Cap and Delta Ring The Solid Quad Rail provides the steady platform attaching: Optics, Lasers, Flashlights, Vertical Grips, Bipods, and other accessories. Very easy to install with four Allen head screws and the provided mounting tool. No gunsmithing required, drop-in fit. Black Anodized finish, Aluminum construction.