Gain Express Digital 1999mV ORP Pentype Redox Meter Measuring range : 0 to  1000mV Accuracy: 5mV / Resolution : 1mV Operating Temperature : 0 - 50C(0 - 122F) Power Supply : 2 x 3V (CR2032) ButtonCell Battery (included) Size : approx. 150 x 27 x 20mm(5.91' x 1.06' x 0.79' inch)