XS Big Dot Tritium is a highly visible, tritium dot front sight surrounded by a large white ring epoxies over the existing front bead sight to help improve target focus and low light sight acquisition and sight recovery after muzzle flash. Ideal for home defense. Installs over front sight beads from .125" - .140" diameter by filling the cavity on the underside of the sight with Brownell's Acraglas Gel, then pressing the sight over the bead and allowing it to fully cure. If existing bead is too small or too large, replace with Brownell's #6 bead for 3-56 threads or #26 for 6-48 threads. Some shotgun barrels may require drilling and tapping of existing hole to 6-48 for installation of #26 Brownell's bead. Bead provided is only for Mossberg Shotguns. Specifications: - Tritium Front Sight Only - Fits: Shotgun with a Bead on Plain Barrel when the bead measures 0.125" - 0.140" - Do it yourself Installation - Sight Color: White/Green - Material: Blued Steel - Finish: Matte Black - Includes: Shotgun Bead (for Mossberg Shotguns Only).