The continuous top rail allows you to mount iron sights, optics and any other accessories without additional rail sections. The Magpul M-Lok system allows users to customize the handguard with rail sections and direct mount accessories. The handguard is constructed of 6061-T6 aircraft aluminum. Coating options available. The MLA has a precision bore to fit the proprietary barrel nut which removes any unwanted play and ensures an exact fit!! Installation requires a 1-1/2" crows foot wrench (not included) for the barrel nut; standard AR-10 barrel nut wrenches will not work with this handguard system. The 15" weighs in at only 12.75 oz. including the barrel nut. PLEASE NOTE: PRODUCT AVAILABILITY AND DELIVERY IS CONTINGENT ON SUPPLIER