1.LCD shows both pH & temp.. 2. with external pH electrode, easy to use. 3.Water proof 4 ... function for freezing the desired value. Supplied with pH 4.01, pH 6.86, pH9.18 buffer.Microcomputer circuit, ... accuracy. Compact size, light weightAuto Calibration for pH 4.01, pH 6.86 and pH9.18Power supply by 1. ... 5 V battery (LR44) x 4 PCsMeter with pH electrode. PT-6020A PH meter ,Pen type digital pH meter