No external power supply is needed.Remains on until you unplug the light or turn off the notebook or PC.Checking seriously and package best before shipping.Directly plug the USB LED lightPackage including:1 x lightinto the USB port on your notebook or PC.Length: 37cm.Power saving design comes with reliable LED light, the light is rated to average 100,000 hours of use.Gently adjust the flexible neck of the light to position the fly light anyway you wish.100% Brand New!Just easily turn on your notebook or PC to power the light.