OverviewThe AC Infinity speed control unit allows you to control the speed of most AC fans that are rated 100 to 125V and have terminal connectors. Some AC fans are not compatible, please read the limitations section. The length of the cord is 6 feet and can be easily attached onto an AC fans terminal. On the opposite end is a standard power plug. Also sold as a bundle with 80mm, 92mm, and 120mm fan models. They include fans with motors that are specially designed to run at various speeds. Please take a look at them in our store. ApplicationsTurn the knob slowly downwards to adjust the amount of voltage that goes into the AC fan. This slows the fans RPM speed, thereby reducing the amount of noise and airflow. You can respond to a range of situations that require high airflow or low noise. LimitationsThe speed control unit works on most AC fans but it does not work well with fans larger than 120mm. As the fans size increases, the amount of speed the unit is able to control will decrease but it can still be used as an on and off switch. Other AC Infinity products to consider (Airflow CFM, Noise dBA): Copy and paste links to view80mm Fan Speed Control Cooling System (4 to 22 CFM, 9 to 32 dBA): http://www.amazon.com/gp/product/B007ZLKCNM92mm Speed Control Cooling Fan System (9 to 36 CFM, 10 to 37 dBA): http://www.amazon.com/gp/product/B007ZLHV8G120mm Speed Control Cooling Fan System (20 to 69 CFM, 16 to 38 dBA): http://www.amazon.com/gp/product/B007ZLFENU