Ewin Digital Pocket PH Meter Water Tester Pen LCD Monitor Pool Aquarium Laboratory Digital pH Meter Tester Easy to use Range: 0.0 - 14.0 pH. Resolution: 0.1 pH Accuracy: 0.1 pH (20C), 0.2 pH Working temperature: 0 - 50C (32 - 122F).Powered by 3 x 1.5V button batteries(not included)