Light up your bike and light up the night. No batteries required! Arara Wheel Bike Lights are powered by frame-mounted magnets. Each light features an LED and a capacitor that passes through a set of neodymium magnets and gets a charge using magnetic induction. Obviously, the best part is how great they look while you are flying down the street. You get two lights for each wheel. They turn on when the wheels start rolling and will dim after you come to full stop. Choose from six colors.