The EZ Twirl Ad car top sign spins in the wind as it sits atop the vehicle. The plastic coated magnetic base attaches easily and strong yet won't scratch painted surfaces. It is 6 1/2" X 17" and can hold 3 inserts(sold seperately). Each message insert is made of durable, flexible plastic and is 5" tall x 14" long. Inserts can be ordered individually (each Twirl-N-Ad requires three inserts). Inserts can be easily changed and are reusable. 40 different messages available.