The TFX features fully-protected TFO technology encapsulated in a virtually indestructible configuration, impervious to oils, chemicals, cleaning solvents, and ultra-sonic cleaning processes. These sights provide unmatched visibility in all shooting conditions, 24/7, utilizing Swiss tritium for maximum brightness. Glowing in the dark without the use of batteries, the concealed fiber cannot be seen by target. Additionally, Tru-Glo's Fortress Finish provides a permanent protective coating for maximum protection and this snag-resistant design fits standard holsters. This model has a fixed front with a F.A.S.T rear and is compatible with Glock 17,17L,19,22,23,24,26,27,33,34,35,38,39,45 excluding MOS models.