Just because the light's not perfect doesn't mean your aim shouldn't be. Troy Industries' TRITIUM BattleSights are designed for twilight or any low-light situation. TRITIUM is a form of hydrogen that emits a continuous light source where using batteries or electricity is not possible. The front post is centered between two Tritium points of reference to allow proper alignment, eliminating the poor sight orientation that is typical in twilight. - Front Fixed Tritium HK Style BattleSights made by Troy Industries - Black Note: Sight is designed to work on same plane rail systems only. Will not work with a railed gas block that is higher or lower than the receiver.