Cabinet Air Control 12-Volt Trigger-Controlled Multi-Speed AV Cooling Fans This cooling system is designed to be mounted in your stereo or home theater equipment cabinet. It will quietly exhaust the hot air outside, or pull cooling air into the cabinet, or both -- you choose how it is set up. It has two fan units, each with 2 high-quality, low-noise 80mm fans mounted together (4 fans total). The system includes a 12 volt trigger control module, which turns the fan on and off, under the control of your component's 12v trigger socket. The 12v module controls the power from the multi-voltage transformer (included with the cooling system), which runs the fan at any one of 5 speeds. Please consult your component's manual for details about how its 12v trigger operates. The fan units are connected by a 2-way power distribution cable, which allows you to separate the fans by up to 7 feet apart. The 80mm dual-fan cabinet cooling units measure approximately 4-5/8" high x 8" wide, which includes the mounting plate. The required hole is approximately 3-1/4" high x 6-5/8" wide. The unit is 1-1/4" thick behind the mounting plate, and only requires about 1/3" additional space behind the back of the fan to allow for airflow. Recommend fan speeds for this system: The two 80mm fan units (running together) are rated at 22db, while moving 112 cubic feet of air per minute (at 3/4 speed). They have approximately these specs at different speeds: 1/2 speed = 74CFM at 16db, 2/3 speed = 98CFM at 19db , and full speed = 148CFM at 25db (approximate). With component cooling, slow (and quiet) are the way to go!