... for freezing the desired value. Supplied with pH 4.01, pH 6.86, pH9.18 buffer.Microcomputer circuit, intelligent function, high accuracy. Compact ... size, light weightAuto Calibration for pH 4.01, pH 6.86 and ... by 1.5 V battery (LR44) x 4 PCsMeter with pH electrode. PT-6020A PH meter ,Pen type digital pH meter