Rail Kits designed for JP system, will also work with many other free-float tubes. Modular handguard/rail system gives the tactical shooter maximum flexibility to customize the number, position, and length of accessory rails on his rifle. Mount rails or sling swivels at 45Adeg intervals around the handguard. Mfg: J P Enterprises SPECS: 6061 T6 aluminum, hardcoat anodized, matte black. Steel inner barrel nut, swivel studs, and setscrews with matte black oxide finish. 2" (5cm) dia. without attachments. Includes inner and outer barrel retainer nuts and 2 sling swivels with backer plates, setscrews.