A 1.3 inch i.D.Will accommodate most low-profile gas blocks.Some interference with clamp-on style low profile gas blocks is possible.Mlok slots at the 3, 6 and 9 positions are manufactured to magpul standards.This ensures proper fitment with any magpul certified accessories.Every ar10 & ar15 foundation handguard comes with a pre-heat treated, 2 inch length 4140 steel barrel nut.This ensures rigid, rock-solid accessory mounting.The barrel nut has been nitrided, not phosphated.Mounting instructions and hardware are included with every ar10 & ar15 handguard.Material: 6061-T6 AluminumFinish: Black Hardcoat AnodizedFree Floating: Yes