Receiver/Amp cooling fan with Super Airbase, thermoswitch & multi-speed control This 120mm Super-base fan unit is designed sit on your component's top air vents, and it provides serious cooling at an economical price. It has a special raised air-chamber base, which covers over 50 square inches of your component's top vents. Hot air is removed from your component over the full area of this large raised base, which causes cool air to be pulled up from the bottom vents. A temperature-controlled thermoswitch module monitors the temperature on top of your component, and turns the fan on and off automatically at approxmately 82F. Just place the thermoswitch heat collector over a warm spot on top of your component's air vents, and it will do the rest. In addition, you control the speed of the fan, with the 5-speed power controller. Recommended fan speeds for this system: The fan is rated at 10db while moving 25 cubic feet of air per minute at 1/3 speed, or 13db & 37CFM at 1/2 speed. With component cooling, slow (and quiet) are the way to go! Other available speeds: 2/3 speed = 16db/49CFM, 3/4 speed = 19db/55CFM, full speed = 22db/74CFM. The fan unit is 7-1/2" square, and 1-1/2" tall, including the top grill and airseal base, and only requires 3/8" of space above for air flow.