The San Tan Tactical STT-15L Lower weighs 7.7 oz and accepts all Mil-Spec AR-15\M16 components and lower parts kits, excluding the ambidextrous controls. The STT-15L Upper weighs 6.9 oz and works with all Mil-Spec AR-15\M16 components including all known handguard options currently available. It features a true hand matched receiver set with the upper serialized to match the lower serial number, a 1.38" integrally machined magazine well flare, and a short throw bullet pictogram safety selector markings marked.