Radical Firearms FR16556SOC15SHR: The Radical Firearms 16\" 5.56mm AR rifle uses MIL-STD Upper and lower receivers along with Radical\'s 15\" MHR free float rail system for increased accuracy, keeping your hands cool, and giving you plenty of room for accessories. The B5 Grip and B5 Stock provide a comfortable hold on the rifle whether prone or upright. Regardless if its your first or fiftieth, a Radical Firearms AR rifle will not disappoint!