Our STT-15L has been designed for those who participate in 3-gun, hunting, or any other shooting activity where weight is a concern. The STT-15L Lower weighs 7.7 oz and accepts all Mil-Spec AR-15M16 components and lower parts kits, excluding the included ambidextrous controls. The STT-15L Upper weighs 6.9 oz and works with all Mil-Spec AR-15M16 components including all known handguard options currently available.