The innovative design of Isotherm's Isotemp Water Heaters represents a welcome departure from traditional upright cylinders and box-like designs of the past.Designed specifically for marine use, these water heaters boast inner and outer tanks made of 316 stainless steel, NOT corrosion-prone aluminum. They may be mounted vertically or horizontally and are secured by stainless steel mounting feet.Engine water heat exchanger coils are extra long for faster heating and AC heating elements are nickel-coated copper for long life. All models feature polyurethane foam insulation for extra heat retention and incorporate service thermostats set to 160F. Thermostatically controlled mixing valves prevent scalding, and ensure that water reaches the tap at the temperature you wish. For installation and operation, see the Isotemp Basic, Slim and Slim Square Installation and Operating Instructions.Key Features Inner and outer tanks made of corrosion resistant 316 stainless steelMount vertically or horizontallyExtra-long engine water heat exchanger coils heat water fasterAC heating elements nickel plated for long lifePolyurethane foam insulation for extra heat retentionThermostatically controlled mixing valves prevent scalding