The XS DXT Big Dot tritium night sight is the ultimate defensive sight set. It features a Big Dot Tritium front sight and express rear sight with a vertical tritium stripe for fast sight acquisition in all light conditions. Big Dot demands your attention - even in high stress and for those with poor eyesight, aids in rapidly achieving combat effective hits. White dot reflects ambient light for best visibility in low light. Shallow V-Notch rear provides an unobstructed view of the front sight, along with a greater field of view down range, especially when moving and shooting. Day-Light, Half-Light, or Low-Light, just "dot the i" and center the dot over your target within 15 yards. Outside Diameter Big Dot 0.188"; fits in common holsters. NOTE: This model does not fit the Springfield Hellcat OSP models.