The Zalman PWM Mate Fan Speed Controller provides quality Fan Speed control with its 3-step Automatic Mode and a Manual Mode. The Zalman PWM Mate Fan Speed Controller modulates the PWM(Pulse Width Modulation) fan speed control signal allowing user defined PWM fan speed settings. The 3-Step Automatic Mode and a Manual Mode provide flexible customization of fan speed control according to the user"s environment. The Mode Switch Button, Manual Speed Dial, and Mode Indicator LEDs provide convenience and ease of use. The Zalman PWM Mate Fan Speed Controller is made with Environment friendly materials incorporated for RoHS(Restriction of Hazardous Substances) compliance.