The BEAMSHOT RF9 mount Creates a standard 1913 picatinny rail system on bull barrel long guns * Included in the RF9 kit are 4 different size spacers * Fits on all round barrel type firearms; Ideally suited for 12, 16, 20, 28 gauge shotguns and all kinds of rifles * Makes it easy to mount Beamshot laser sights, tactical flashlights and other types of accessories on your firearms