Does your fan has built-in speed settings? If yes, then DON'T buy this product, it won't work with your fan. If your fan doesn't have speed settings, then this product IS for you and will allow you to control the speed of your fan. Hydro Crunch Variable Fan Speed Controller allows you to control the speed of fans built with a Brushed Motor, which don't come with built in speed settings. This fan motor speed controller will help you to reduce the noise from your intake booster fans, duct fans, exhaust fans, centrifugal fans, etc. Depending on the type of the motor used, this speed controller will be effective in decreasing the max output CFM of your fan by 20-50%. Reduced airflow equals less noise and more privacy in your grow room. Your fan's adjustable range could be determined by rotating the knob of the Hydro Crunch Variable Speed Controller from the HIGH setting towards LOW setting until you start hearing fan's motor hum. Do not decrease the operating speed of your fan past the "hum" point. Hydro Crunch Variable Fan Speed Controller is not suitable for Non-Brushed motor fans, as well as fans with built-in speed controllers.