Bcm free float quad rail eliminates loads from barrel, reducing the deflection for more accurate shooting.Precision machined aerospace 6061-t6 aluminum alloy, for high strength and lightweight with a proprietary engineered profile offers additional cross sectional strength.Features a steel barrel nut to resist movement under heat.Diameter inside is 1.30", outside 2.12".Includes four qd sing swivel sockets and mounting hardware.Rails: PicatinnyType: HandguardFirearm Type: AR RifleFirearm Model: AR-15Material: 6061-T6 AluminumFinish: Black Hardcoat AnodizedPositions: 4Free Floating: Yes