The HI73127 spare pH sensor makes electrode replacement quick and easy. The spare pH sensor is designed as an easy-fit cartridge that locks into place, featuring two o-rings to maintain a watertight seal. With no pins to line up or that can break, this sensor is ideal for quick replacements.
 
More details about Hanna HI73127 Probe PHEP4 & PHEP5 & Combo:
The HI73127 is a spare pH tester electrode that is compatible with:
HI98129, and HI98130 Combo multiparameter testers
HI98127 and HI98128 pHe® testers
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.