Well this is my first product from dynamat I am really pleased.

It came with a 4x10 piece of dynamat extreme, and 4 little foam pieces to put on the back of the license plate frame to reduce rattle. It does a great job you cant hear anything but a little tap since the cobalt only has two holes to use to screw on your license plate. Here is one of the pictures i took

 

Foam weatherstrip tape and 2 more screws does a better job for less. Dynamat belongs on the inside of the trunk.

 

True but it does help it from bouncing off the bumper like it did. Thats all I wanted..

The other stuff would have done it, but not like this

 

Whatever works. There is no excuse for a license plate rattle. It's a cheap and easy fix any way you do it.

 

cheapest and fastest fix it jsut bend the bottom of the license plate out away from the car. No more rattles.

 

maybe im just lucky but i have never had my license plate rattle. and ive had/ tested tons of different speakers and setups in my car