USB fan air volume adjustment, stepless speed regulation, and arbitrary adjustment of weak and strong winds. This small USB device voltage regulation module increases the voltage by adjusting clockwise and reduces the voltage by adjusting counterclockwise. It is suitable for 5V USB fans on the market and can be installed on the notebook computer radiator fan. It also supports mobile phone chargers, USB power , and computers with USB interfaces. It is small and can be carried around, does not take up a lot of space, and is easy to carry. The output voltage range of this stepless speed regulator varies between 2.5V and 7.5V, and the air volume can be set arbitrarily, with a wide range. The clockwise knob can increase the wind speed, and the counterclockwise knob can reduce the wind speed. The knob has a switch function. Input voltage: DC4V~12V Output voltage: DC2.5V-7.5V Rated power: 5W (do not overload) Colour:Black Material:plastic Package Contents: 1 x USB Speed Controller Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.