Rail for AR15 Plastic Handguard is Picatinny MIL-STD 1913 tapered to match the handguard of the standard GI carbine and M4 handguards. Black anodized aluminum construction. Rail includes two mounting screws and flanged nuts. Allen wrench tool also included. Length: 5.9" The taper in the rail will make accessories mounted to the rail parallel with your bore. More mounting holes for flexible mounting and increase ventilation. The ends of the rail have been rounded off for more comfort and to make it less snag prone.