Installs Easily Over The Existing Bead Sight 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. Installs over front sight beads from .125" - .140" diameter by filling the cavity on the underside of the sight with Brownells 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 Brownells #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 Brownells bead. Plain Barrel model with cupped bottom fits round shotgun barrels. Includes instructions.