Advanced design, superior sighting and BattleReady(TM) toughness define Troy Industries new Di-Optic Aperture (DOA(R)) flip-type sights. Now available with Tritium, a form of hydrogen that emits its own light source, ideal for any low-light shooting situation. These sights provide lightning fast target acquisition and are manufactured to exceed military specs. The optically engineered apertures center your eyes instantly and effortlessly providing a clearer target picture than with round apertures. The sights feature two settings, one for up to 300 meters and a second for up to 550 meters. This versatility makes the DOA ideal for military, law enforcement and home defense applications. These advanced sights have been extensively field-tested and, like all Troy Industries products, are BattleReady. Count on it.Features : Sight is designed to work on same plane rail systems only Will not work with a railed gas block that is higher or lower than the receiver