Feature:1. You can adjust the wind power at will.2. Turn the knob clockwise to increase the air volume, counterclockwise to reduce the air volume, and the knob with switch function!3. The stepless governor output voltage range varies from 2.5 to 8.0V, and the air volume is arbitrarily set! And the range is wider!4. Suitable for common 5V USB fan in market.5. Suitable for multiple power supplies such as computer,power bank and etc.Specification:Item Type:Fan Speed ControllerMaterial:AluminumInput Voltage:DC4~12VOutput Voltage:DC2.5~8.0VRated Power:5WPackage List:2 x Speed ControllerNote:How to use: Insert the governor into the mobile phone charger, power bank, computer USB, etc., plug the fan and plug it into the governor! Or use Micro USB 5.0V to supply power.For two-speed fans, please put the fan in one gear, otherwise you may not be able to adjust the speed!