If you need a fan controller just to vary the speeds of a 3 wire fan and don't care about anything else, this controller does the job. The speed control is not a smooth progression from 0% to 100%, but it seems to work well enough that it shouldn't be too much of an issue unless you need super fine speed control. If, like me, you have a fan that's stronger than you need and want to reduce the speed in order to reduce fan noise, look elsewhere. It appears to be a low frequency PWM controller which causes the motor to make an awful squealing/whining sound when not at full power. I ended up using an Arduino and a motor driver in its place (which I was trying to avoid by buying this), and this is collecting dust on my shelf for the foreseeable future.

The controller works, but if I turn the fans down to anything less than about 90% speed the fans make an awful high pitched whining noise. The construction of the product seems solid, however I would not recommend this product for controlling 3 pin fans. I have not tested with 4 pin or 2 pin fans so I can't comment on those. I believe the controller is running a duty cycle on the voltage output instead of just reducing the voltage via resistance, thus leading to the noise.

This fan speed controller works well. It has a connection that will work with 2, 3, and 4 pin fans. Would buy another one or two, but they seem to be out of stock often.

This fan speed controller works well. It has a connection that will work with 2, 3, and 4 pin fans. Would buy another one or two, but they seem to be out of stock often.