The Extech EC505 Replacement Dissolved Oxygen Module for use with the Extech EC500 Waterproof ExStik II pH/Conductivity Meter and is easy to clean. Additional features include a rugged flat surface pH electrode/conductivity cell module, a screw-on membrane cap for easy replacement, and ATC via built-in Pt-100Ohm sensor. The EC505 measures conductivity, dissolved oxygen, TDS, salinity, pH and temperature and is non-interchangeable with ExStik pH, Chlorine or ORP meter.