Multi-line hold function / The mounting direction of the main unit can be placed vertically or horizontally for a clean arrangement. Safety device / Shuts off the power supply when heating in the air (when the safety device is activated). Safe design: The body is made of self-extinguishing resin that does not ignite and the cover is made of aluminum for added safety when empty firing (heating in air). Small heater comes with a ultra-small controller. Set freely from 68°F to 98°F (22°C) with the dial. *There is no function to cool the water temperature. LED indicator/power on status with LED illumination for easy viewing; Compatible water tank quantity: 3.9 - 3.9 gal (10 - 15 L); For indoor aquarium; Heater part size: W 4.9 x H 2.2 x D 1.2 inches (12.5 x 5.5 x 3.0 cm) / Controller part (W 6.3 x H 3 x D 2.3 cm).