The USB Fan with non adjustable wind is a 5V direct supply fan motor, while the fan with two gears has a boost circuit board inside. When it is placed in the second gear, the boost board raise the 5V of USB and then connect the motor, and the air volume be large! The output voltage range of the stepless governor changes smoothly from 2.5V to 7.5V, and the air volume is set arbitrarily! And range! Turn the knob clockwise to increase the air volume, counterclockwise to reduce the air volume, and the knob has a switch function! usage method: Insert the male head of the governor into the mobile phone charger, charging treasure, computer USB, etc., and then insert the fan plug into the female head of the governor! Power supply range: DC 5 ~ 12V Output range: DC 2.5 ~ 7.5V Rated power: 5W! (do not overload) matters needing attention: When it is used to adjust the fan in two gears, please put the fan in the , otherwise it may not be to adjust the speed! Color: Blue Material: PCB+Plastic+Metal Package Contents: 1* USB Fan Governor (Knob color is random) 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.