Caston USB Powered 2-Mode Speed Adjustable Double Blades Mini Desk Fan Portable Ultra-Quiet Cooling Fan for PC Laptop Notebook(Blue) 1.Dural-motor: two fan blades rotate in opposite directions driven by different motors to produce strong blow and low noise. 2.Low-noise: motors work very quietly, and the noise is produced from the blow below 40dB as quiet as in a library environment. 3.Adjustable blow strength: a knob switch is designed for adjusting blow strength at two levels(0-stop, 1-weak, 2-strong). 4.Adjustable blow direction: the fan can be adjusted from 0 to 45 vertically. 5.Easy to carry: the size is very small and the weight is only 6 ounce. It's easy to carry by one hand.