The magnets can be placed on any metal surface. Some cars are manufactured with fiberglass or other non metals so they will not adhere to the parts of the cars that are not metal. Care for the magnets is on the packaging and on our web site. Do not apply a car magnet to a brand new car- has to have the paint cure for at least 90 days. Always clean the magnet backing and the car before applying. They can also be used on any other metal surface like mailboxes, refrigerators, filing cabinets, lockers etc. If in doubt about your car call the dealer to find out what areas of your car has metal and what it is made of. Hope this helps! Thanks and enjoy your grandogs!