A "must-have" for every boater. Whether your boat is docked, in the open water, or at home, you should have On-Board ProMariner's Hand Held DC System Tester. This easy use tester includes 6 L.E.D read out indicators. Test the condition of your batteries, alternator & regulator and battery charger quickly and easily. Our hand held tester is small and light enough to fit in your pocket.