The A.R.M.S.® #40™ 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 in 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. Has horizon line notch 500-600 meter sight. Windage adjustments .75 MOA.