Specifications and Features:Midwest Industries Combat Rail MI-CRM9.259.25" One Piece Free Float Hand GuardContinuous MIL-STD 1913 Picatinny Top RailSeven sides of M-LOKTwo Integral Anti-Rotation QD Sling SocketsSuper Slim 1.5" Outside Diameter1.3" Inside DiameterFully dehorned/deburred4140 Heat Treated Barrel NutPatented 4140 Heat Treated Torque Plate6061 Aluminum with Type 3 Hard Coat Anodizing100% Made in the USA, by American's for American'sManufacturer Lifetime WarrantyMatte Black FinishIncludes:Free Float Hand GuardBarrel NutBarrel Nut Wrench5 Slot Polymer Rail (M-LOK to Picatinny)Fits:Mil-Spec AR-15 Forged Upper Receivers or Midwest Industries Billet Upper Receivers ONLYNote: Due to the many different dimensions of Billet Upper Receivers from various other manufacturers compatibility with those billet uppers is unknown.Note:NOT for use with Gas Piston AR's for use with direct gas impingement AR systems ONLY.