For 12 gauge only. The best way to carry six extra rounds in the most convenient and accessible location for quick reloading without losing sights. Mounts directly to the receiver and holds the shells securely. Installation is easy and all mounting scews are included. In most cases no alterations to the shotgun and no gunsmithing are required. Made from aircraft grade aluminum. Shell holder is injection molded from durable polymer that resists moisture and extreme temperatures. The Remington 870 Express and Wingmaster require modification to the forend. Tacstar