Extech DO603 Membrane Kit for ExStik Dissolved Oxygen MeterExtech DO603 ExStik Flat Surface Electrodes ExStik Flat Surface Electrodes Rugged, flat surface electrode provides On the Spot measurements with an ExStik meter Ideal for direct contact applications such as food, paper, cement and wet surface Key Features: Flat surface electrode allows On the Spot measurements whether the sample is liquid, semi solid or solid Chlorine and pH electrodes have built in temperature sensor Chlorine electrode does not