This solar LED road stud is naturally charged by the sun. As soon as it starts getting dark the LED lights in the stud come on automatically each night and remain illuminated for up to 24 hours. The stud has been specifically designed to improve roadway safety and can help to prevent serious accidents. They are also ideal for illuminating paths, decks and docks. We recommend using this product for the following areas: 1. Dangerous blind corners and sharp-curves, black spots and poorly lit areas. 2. Areas with unpredictable weather conditions (coastal roads, foggy areas, wet and rainy regions, etc.). 3. Joint intersections, on and off ramps, center lines and dividers, entrance warnings, carpool lanes, bridges, cross and side walks 4. Guidance lines, traffic islands, roundabouts and mountain roads. 5. Taxiways at airports, bike and pedestrian lanes, aboard ships and watercrafts. 6. Entertainment areas, parking lots, hotel entrances and gas stations etc. 7. Decks and Docks 8. Paths and Driveways 9. Fence Posts 10. Bike Trails They can even be seen from a distance of up to 850 yards!!! They are cost effective, easy to install and require absolutely no wires or maintenance.