The Milwaukee MW600 PRO Portable Dissolved Oxygen meter is one of Milwaukee's most popular meters with its reliable and fast operation as well as its accuracy. The Milwaukee PRO DO Meter is preferred by people looking for lab level accuracy without the cost. The Milwaukee DO Meter is popular with everyone from field biologists and educators to fish farmers and koi pond owners. Design Features: Fast, easy-to-read, results with large digital LED readout, Repeatable, accuracy to ±1.5% FS, Lightweight and portable, Simple 2 point open air calibration, Uses MA840 reinforced polarographic probe with an oxygen-permeable polytetrafluroethylene (PTFE) membrane sensor, 5 o-rings, membranes and one protective cap included, 10 feet probe cable for extra flexibility when testing, 70 hours of battery life with continuous use (battery included) with low battery warning.