Troy’s new SDMR Rail installs quickly and easily. The streamlined one-piece design is exceptionally lightweight and sleek. With its series of keyholes, accessory mounting is simple and reliable: they can’t loosen or fall off. Machined from hardened aircraft aluminum with stainless steel components and finished in MIL-SPEC hardcoat anodizing. Will mount on standard AR15/M16 mil-spec barrel nut. Barrel nut not included.