Use Ultra Bright Flashing Tire Sparx to streak through the dark night like cosmic debris! Make your surroundings aware of you on your rides after dark by using LED Lights on your tires. These fast Blinking Lights help to keep a night cycler safe and visible. They are motion activated; the LEDS will stay flashing as long as there is constant movement. If the tire is still the lights will automatically turn off after 10 seconds. Ultra Bright Flashing Tire Sparx screw into Schrader valves, if you have Presta valves an adaptor can be found at your local bike shop. Each stellar pack includes 2 Tire Sparx as well as 6 replacement batteries!