HI 98121 is a waterproof meter that measures pH, ORP and temperature. The housing of this tester has been completely sealed against humidity and are designed to float. Electrode replacement with the stainless steel round connector means there are no pins to bend or break during replacement. When the cloth junction becomes clogged and response time is sluggish, simply pull out 3 mm ( 1/ 8” ) to clear the clogging which will improve response time and stability. The exposed stainless steel temperature sensor on these models facilitates faster and more accurate temperature measurement. Order Information: HI 98121 ( ORP/ pH) is supplied with HI 73127 pH electrode, HI 73128 electrode removal tool, batteries and instructions.