Sound Deadening

Theres a lot of sound deadening products available, I decided to go with MAT 66. The mats are 80 mil in thickness and cover 36 sqft of area per box, I used 2 boxes on the Firebird. Manufacturers of sound deadening products recommend covering a minimum of 25% of interior surfaces and up to 60%, I covered 100% of ceiling, interior floor, trunk floor and door skins.