Enviro-Equipment AutoCal Calibration Solution AutoCal Solution (pH 4.000, 0.0 NTU, 4.49 mS/cm) for pH, turbidity, and conductivity. Typically used with HORIBA water quality instrumentation. SKU AUTOCAL-250ML $8.99 Select product AutoCal Calibration Solution, 250 mLAutoCal Calibration Solution, 500 mLAutoCal Calibration Solution, 1 LAutoCal Calibration Solution, 4 L Quantity