The Replacement Electrode is the spare pH electrode for the HI-98100 Checker Plus pH meter and the Groline pH Tester. Replacing the pH electrode is both quick and easy. Simply unscrew the old probe and fit the new one.Replacement Electrode is a single junction pH electrode with a slim 8mm polypropylene body that easily fits into test tubes and other small-sized vessels.Can also be used with the Checkfridge® Remote Senor thermometer.