The specially designed screw-in Silver/Silver Chloride Half Cell is for use in the Buckleys / Roxby BathyCorrometers and UCP1A and UCP1B underwater probes. The Half Cell can be easily replaced in these units as it has a screw-in fitting. The water-tight seal is made by the use of an 'O' ring. The electrical connection to either a Bathycorrometer or a UCP probe is made by a silver plated 3mm plug. The electrode is housed in an acetate body. Holes in the body allow the easy flow of water, thereby removing any debris that might contaminate the electrode. Providing the storage instructions are followed, the Half Cell will give a service life of up to two years.