TRUGLO Brite-Site Tritium/Fiber Optic Sight, Fits Glock 17/17L/19/22/23/24/26/27/33/34/35/38/39, Green and Yellow TG-TG131GT1Y When you need to make a fast and accurate shot" brightness counts. They brought fiber-optics to the shooting sports industry years ago for this very reason. They have now paired them with their tritium night sights to create a consistently bright sight picture-day or night! Their patented combination of Tritium and Fiber-optic technologies unites the best of both worlds. Whether you are in glaring daylight or complete darkness" you can count on TFO(R) to provide a bright and reliable sight picture.