The Big Dot Tritium - Mossberg Shotgun, Bead on Plain Barrel from XS Sights are defensive tritium sights designed to enhance your defense gun. The sights use a proprietary photoluminescent Glow Dot that absorbs ambient light and glows in low light. The convex dot's additional surface area increases light absorption, intensifying the charge of the Glow Dot. Designed to be large and highly visible, these sights help solve many issues