TFO Sight Set Tritium - TG131GT1A The Tritium maintains the brightness level of the sight in low-light (or NO light) conditions. That means that sight can be seen even in complete darkness with perfect transition through all lighting conditions. Tritium does not need batteries and does not need to be charged with light-it simply glows! Product Specs: Uses the patented TFO technologyUnbelievable transition through all light conditionsGlows in the darkNo batteries requiredCNC-machined steel constructionConcealed fiber cannot be seen by targetFits standard holstersSnag-resistant design