?Customer Service?: Provide free online customer service. We promise to answer within 24 hours . If you have any questions, please feel free to contact us, we are willing to answer your questions. ?High Compatibility USB Power?: SmartDevil USB fan is powered by USB and is compatible with PC / laptop, mobile power, AC adapter, car charger and other USB supported power. USB fans save energy and protect the environment. (Note: This fan has no battery). ?Infinitely-variable Of Speed Control Knob?: Unlike the traditional wind speed adjustment button, this fan adjusts the wind speed through a 180-degree adjustable knob. The wind speed changes smoothly with the rotation of the button. You can choose the most comfortable speed according to your needs. ?Adjustable & Easy to Clean?:Small, light and convenient personal fan with 20-degree adjustable valve body, the wind direction can be changed as required. Can circulate indoor air and balance room temperature. The rotating fan cover extends the distance of the draft shield. Detachable design, rotate counterclockwise to remove the mesh cover, easy to clean. ?Small But Powerful?: The size of the fan is: 5.23 inch. Although it is small but the wind is powerful. It has 5 streamlined fan blades to reduce noise, reduce wind resistance and increase air supply area. Ideal for home, car, office, desktop, camping or travel.