The HI73127 is a spare pH tester electrode that is compatible with: HI98129, and HI98130 Combo multiparameter testers, HI98127 and HI98128 pHep® testers, and HI98121 ORP tester. These meters also use HI73127 replaceable electrode that has a stainless steel round connector and extendable cloth junction. This cartridge design has no pins to line up or that can break.