Extends past the rear of the slide slightly to extend the sight radius for increased accuracy. Really like how low it is and looks great on my full size. Focuses your eyes to the center. Paired it with a Dawson fiber .115 sight and appears a .205 tall should impact directly behind the fiber dot with 124 gr. Federal at 15 yards since the .220 height was grouping tight an inch and a half low. So should be POA/POI at 25 yards with the shorter height. Great quality and is smaller than the same sight for Glocks.