The Reef Octopus USB Smart Fan will automatically increase or decrease the fan speed depending on the ambient temperature of the area surrounding the thermostat. Makes and excellent choice for aquarium canopies, enclosed stands & equipment cabinets to help regulate the temperature within. Keeping these areas cool will help reduce heat transfer into your aquarium and avoid dangerous temperature spikes while also ensuring long lasting performance of your equipment. Fan will increase speed at 90 degrees F and continue to increase until full speed at 110 degrees F where it will reach its maximum CFM. Available in a 3in and 4in model. Features Automatically ramps speed based on temperature USB power end with safe low voltage power adapter Plug and play operation 16" thermistor cord NOT INTENDED FOR CONTINUOUS USE. Fan is rated for 2000 hours.