When using the Emergency Highway Flasher you'll be clearly visible up to 2000 meters / 1.25 miles away. This Emergency Highway Flasher is water resistant and measures over six inches long and four inches wide. It uses eighteen super bright LEDS which can be either remain on or flash in order to warn or signal approaching cars. Two rare earth magnets are used to attach it securely to the back of a car, truck, bicycle, or any metal object. This new type of magnet is smaller and far superior in strength to regular magnets. Also includes a built-in stand. Requires four (4) 'AA' batteries that are not included.