The XS Standard Dot Night Sights are designed to enhance your defensive revolver. The sights use a tritium lamp coupled with a proprietary photoluminescent orange or green 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, from aging eyes to deteriorating vision. XS Tritium Night sights are big, bright, and easy to see day or night! The XS Sights Standard Dot for the Taurus 856 and 605 revolvers fits guns with a factory pinned in front sight. The replacement sight is pre-drilled for the Mfg: Xs Sight Systems