XS Sight Systems tritium standard dot fits Colt Viper revolvers. The front sight features a bright tritium vial and is paired with a photoluminescent glow dot. The high contrast sight picture will increase your sight acquisition speed and accuracy. The dual illuminated front sight provides high contrast in bright light and the glows in low light. XS Sights are a superior upgrade over the factory brass sight. FeaturesTritium powered front sight Standard Dot front measures 0.140"High-contrast colored front sight Glow dot absorbs ambient light and glows in low lightDurable CNC machined steel