The TRUGLO TFO sight are the most revolutionary innovation since TRUGLO, Inc. introduced fiber optics. TFO refers to our patented combination of Tritium and Fiber Optic technologies. The Tritium maintains the brightness level of the sight in low-light (or NO light) conditions. That means you can see your sight 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! FeaturesPatented TFO technologyCNC machined steel constructionSnag-resistant designNo batteries required DISCLAIMER: This product is not manufactured, authorized, endorsed, or warranted by GLOCK. GLOCK does not warrant or represent that this product is compatible with GLOCK pistols.