The HS503CU is a small compact red dot sight with the option of a 2MOA dot only or a 2 MOA dot with a 65MOA circle reticle pattern. Employing LED technology, the life time for one CR2032 battery can reach 2 years if left on constantly. However, the solar technology and automatic brightness features work together to extend the battery life dramatically beyond that for the average shooter. The U signifies a housing design that shrouds the windage and elevation turrets on two sides. The sight may be installed on various firearms such as shotguns, pistols, rifles, air rifles and crossbows.