Range 0.0 – 19.9 ppm O2/l , Resolution of 0.1mg/L, Unit gives 1.5% Full Scale Accuracy, Includes a MA840 Polarographic D.O. Probe with 3 Meter Cable, Spare Membranes, Starter Bottle of MA9071 Electrolyte Solution, Screwdriver for Calibration & a 9 V Battery ( Recommended Calibration Procedure is "Open Air" )