Truglo offers handgun owners the ultimate target/defensive sight with their patented TFO (Tritium Fiber Optic) technology. The tritium maintains the brightness level of your sights in low light or no light conditions. The fiber optic light rod provides superior performance in low light to bright light conditions. The combination of the two provide unbelievable transitions through all light conditions. Fits the following Glock pistols - 20,21,29,30. Additional features include; Tritium (glow in the dark) green front/green rear 3 dot design. CNC machined steel construction. Concealed fiber can be seen by the shooter only. Fits standard holsters. Snag resistant design.