XS Sights XS Big Dot, Tritium Night Sight, Front Sight Only, Tritium Center and Orande Outline, Fits Shotguns with 125 - .140 Diameter Bead, Includes Replacement Bead for Mossberg Shotguns SG-2005-3N XS Tritium Night Sights offer the best front sight visibility in all lighting conditions" combining tritium with XS' patent pending glow dot. Upgrade a home-defense shotgun to a high-contrast front sight that absorbs light and glows in less than ideal conditions. Optic Orange is designed to offer a high-contrast sight picture when shooting in bright light conditions and maintain its visibility in decreasing light levels. To ensure visibility in low light when uncharged" optic orange is primarily based on yellow with a hint of red. The increased surface area of the convex dot increases light absorption" intensifying the charge of the glow properties of the dot. These sights require a .125" - .140" diameter bead. Kit comes with replacement bead for Mossberg shotguns. If current shotgun bead is not in that diameter range and is not a Mossberg" Brownells #6 or #26 front bead will need to be purchased and installed before XS Big Dot. Installs with any two-part epoxy" like JB Weld.