By moving the hinge for the sighting mirror to the center of the base plate, users are now able to sight objects faster and more accurately along the same direction of travel mark used for map navigation. We've also added a meridian insert, so that you still have Brunton's patented tool free declination system, but the meridian lines stay down on the map for greater ease and more precise headings. Features:- BRUNTON O.S.S. alignment system - Tool free declination adjustment - On the map Meridian lines - 2 degree resolution - Mid-hinged sighting mirror - Protective cover - Clinometer - Inch/mm scales Specifications:Weight: 2.2 oz. Dimensions: 2.9?x3.9?x0.8?