You've seen them in the store, probably even had one pass you on the road. They are magnetic ribbons that come in a variety of colors and sizes. It’s a $3 display of patriotism that could cost you much more in the long run, up to 100 times what you paid for it.
The problem isn't with the magnet but with the care you do or don't put into it once it's stuck on your car. Water can get in behind it, build up, and heat up when the sun hits it.
Mike Barry, Body Shop Manager at Shaheen Chevrolet, says the ribbons can scratch the clear coat on newer vehicles which can sometimes be fixed by buffing, but other times the surface will need to be repainted.
Keeping the magnet and the vehicle surface clean can lessen your chances of damage. Barry also suggests you move the ribbon periodically.