The Olight Osight SE Reflex Sight is tough against the elements with a fully enclosed system, ensuring reliable performance in any environment. The aspherical lens ensures zero distortion, parallax-free performance, and exceptional clarity for rapid, precise target acquistion. FeaturesEffortless battery replacement without removing the opticDirect fit to optics-ready slides with seamless integration and exceptional compatibility across multitude of buildsThe low deck height provides a perfect co-witness with most factory iron sights, eliminationg the need for lower 1/3 or suppressor-height sightsCompact and streamlined, the Osight SE stays secure in any IWB position - the ultimate choice for concealed carry or duty useIf the battery voltage is below 2.2V, a 3-blink reticle every minute indicates an immediate battery replacement8 daylight and 2 night vision settings - compatible levels for versatility in any demands