When you need to make a fast and accurate shot, brightness counts. Truglo 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! Truglo 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 to provide a bright and reliable sight picture. Fits S&W M&P (including SHIELD & .22 models, excluding .22 Compact / C.O.R.E. models), SD9 and SD40 (excluding VE models). Please note that yellow fiber-optic is intended to appear less bright than green. Uses Truglo's patented technology The ultimate handgun sight Unbelievable transition through all light conditions Glows in the dark No batteries required CNC-machined steel construction Concealed fiber cannot be seen by target Fits standard holsters Snag-resistant design