The Extech EC405 ExStik Replacement Conductivity Cell Module For Extech Model EC400 is designed for use with the Extech Model EC400 Conductivity/TDS/Salinity Meter. The EC405 is easy to clean, features rugged conductivity cell module, a protective connector cap, ATC via built-in Pt-100Ohm sensor, and measures Conductivity, TDS, Salinity and Temperature. It is non-interchangeable with ExStik® pH, Chlorine or ORP Meter.