"The Sabre-15 Enhanced Ambi Receiver Sets are here! First introduced on the Mixtape Vol. 1, these forged receiver sets match seamlessly and are a perfect base for your next build. The upper receiver features engraved t-marks and provides a thermal fit for your barrel. The lower receiver includes an ambidextrous bolt catch/release and features an integral trigger guard and flared magwell." *The Sabre-15 Enhanced upper receiver is compatible with handguards that index on the front of the upper. Handguards with anti-rotation tabs designed to overlap the upper may not fit without modification*