Zinc based reference cell surface with +/- 30 mV measurement accuracy. Application in salt water or saline water conditions. 20 years nominal lifespan. Dimension: 68 mm diameter and 38 mm thick. Weight: 0.8 kg. 1 x internal fastening bolt. Diver changable. Water proof neoprene incapsulation. Molded backside with embossed sealing rings.