The YSI Pro1020 pH / ORP & DO meter is built for the field; it has military spec connectors, is IP67 waterproof, and the case over molded with rubber, and it has been drop tested to ensure durability. It features a large graphic, backlit display and glow in the dark keypad making it usable in any lighting condition; it's even visible while wearing polarized sunglasses. The Pro1020 also features smart calibration; it remembers the previous calibration values and simply walks you through the routine.