The Troy Industries Battle Sights have set the standard for performance and durability. Now, Troy has developed a rugged low-profile sight designed for firearms with top rails higher than the standard M4. The Troy Industries Micro Battle Sights are also a terrific option for shooters who favor a sightline that's as close to the barrel as possible, or for those with raised top rail systems, the Troy Micro Battle Sight provides an ideal solution. The Troy Micro Battle Sights are rugged, reliable and Battle Ready. The DOA aperture has two settings, 0 to 300 meters and 500 meters. Notes: Troy Industries makes two sights; standard and micro. The measurement to the center of the standard aperture is 1.36". The measurement to the center of the micro aperture is 1.16". The standard sights are meant for Mil-spec top rails and the Micros are meant for the enhanced weapons such as the IAR, Robinson Armament XCR, Heckler & Koch 416 & 417, and other weapons with raised top rails.