Troy DOA Rear Folding Back Up Sights - 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 500 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 Battle Ready. Note: Sight is designed to work on same plane rail systems only. Will not work with a railed gasblock that is higher or lower than the receiver. These sights provide lightning fast target acquisition and are manufactured to exceed military specs. The sights feature two settings, one for up to 300 meters and a second for up to 500 meters. This versatility makes the DOA ideal for military, law enforcement and home defense applications.