The Swarovski EL Range 42 with Tracking Assistant pairs renowned EL optics - 90% light transmission and a wide, bright image - with a laser rangefinder that measures 10 to 2,200 yds to within a yard, including full angle compensation. Its Tracking Assistant marks the point of impact and, together with the smartphone app, walks you to the site when recovering game. A single CR2 battery is good for roughly 2,000 measurements.