12mm x 1.5 Water Temperature Sender from Dakota Digital.
This sending unIt is designed to work with Dakota Digital gauges, to ensure accurate and precise readouts. It is compatible with Odyssey series I & II, as well as Solarix instruments.
It has a range of 0-300 Degrees Fahrenheit ( 0-150 Degrees Celsius ) and a resolution of 1 Degrees Fahrenheit.