I bought this fan controller for a raid array with 4 disks in an enclosure that fits in a 5.25" bay. The noise from the enclosure fan in addition to that from the two CPU fans was getting unbearable. With this fan controller, I was able to reduce the noise from the former to a tolerable level. The controller is set to about the halfway position to ensure that the drives still receive some cooling. Turning the fan controller completely off is probably not a good idea. Overall, a device with great value!