This LCD display gauge has one water tank level gauge and 1 Voltmeter, A water Tank Sender probe/level sensor is required to be purchased separately. (See Below) Description: These new technology gauges have a coloured LCD analogue display with LED backlighting for crystal clear viewing. Five levels are displayed. A 12 volt supply is required. These gauges only draw 50 mA so they can typically be left on without flattening your on-board battery. There is a power on/off switch to turn the gauge off when the caravan is not in use e.g. storage. The LCD water gauge measures H108mm x W108mm x D20mm. The gauges are to be matched with sender probes (sold separately), the sender probes are available in 2.5m 5.0m 7.5m cable lengths. The sender probes are easy to fit and only require one 22mm (7/8") hole in the side of the tank and suits tanks from 100mm to 280mm (4" to 11") deep. The sender probes are sealed by a special grommet which is compressed in the hole when the nut is tightened and measures the water level by contact with the 5 sensors along the arm. The probe has no moving parts.