84-IP General lab and field use 84-IIP for use with pH meter P-IA and PX-IA 87-IP for use with pH meter PH-I 87-IIP for use with pH meter PH-II or lab 87-IIIP for use with pH meter PH-III or lab 88-IP General lab and field use 88-IIPGeneral lab and field use 88-IA General lab and field use 89-I General lab and field use 99-I with double layer. aquarium and fish farming use 99-IA with double layer. aquarium and fish farming use PS-02 skin, fruit, sheet, piece goods and etc. PE-200 General lab and field use with temperature sensor