Tapco TAP22041: Tapco Tritium Sights offer brighter, more vivid, aiming dots. These night sights with the use of Tritium are always on, making them more effective. The Tritium insert is surrounded by a daylight-fluorescing material that produces optimum visibility in daylight. TAPCO\'s sights are optic height offering a lower 1/3 co-witness with your slide-mounted red dot sight. Designed to work as a backup sight for red dots, obscuring less of the optic window while still allowing three-dot sight alignment if needed.