The gardner bender digital battery tester allows you to quickly determine the existing charge in your battery. No more guessing if the battery is good or not. Tests all common batteries to determine if they are charged or need replacement. The tester provides an easy color coded readout. easily and quickly determine existing charge; moveable contact arm fits multiple battery sizes: aa, aaa, c, d, n, 9v, 1.5v button cells; lcd readout with three-color scale: green is full, yellow is low, and red is dead; requires one 1 1.5v button cell battery not included