The A.R.M.S.® Stand Alone Flip-up sight, utilizes the same well proven concept as the rear sight on the SWAN® Sleeve system. The unique design of the spring loaded rear sight, ensures constant battery action and repeat zero. The sight is held in the locked down position by a quick release lever, that prevents the sight from being accidentally engaged, but is as fast as a trigger to release even with arctic mittens. The initial elevation zero utilizes the standard M16/M4 front sight bead. When the sight is released into battery the 250-300 meter aperture is ready for immediate close combat use. For longer ranges the leaf sight aperture is rotated to access the 500-600m capability with the built in horizon line feature that helps lead distant targets and lets the shooter square the rifle to counter windage offsets, if the rifle is inadvertently tilted. Other type rear iron fold-down sights require the shooter to push it into position, which means they can be accidentally knocked down at the worst time. The A.R.M.S. spring loaded flip-up sights never let you down, because they're designed to always be there even when going through brush or being dropped.