TruGlo's Brite-Site TFX features fully-protected TFO technology encapsulated in a virtually indestructible configuration, impervious to oils, chemicals, cleaning solvents, and ultra-sonic cleaning processes. The 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. The TFX Pro sights feature a quick and accurate U-notch design, glow-in-dark sights, a contrast colored front sight Focus Lock ring for even faster focus, and an angled rear sight for one-hand operation. This high mount model is compatible with Glock 20/21/25/28/29/30/31/32/37/40/41 excluding MOS models.