dynamat extreme is good stuff but they rape you for price,
do your research and
http://www.sounddeadenershowdown.com/products/
Dyna mat extreme bulk pack $140 for 36 sq ft $3.88 per ft
Published Thickness (mils) 67
Published Foil Thickness (mils) 4
Raamat 60sqft for $130 $2.16 per ft
Published Thickness (mils) 60
Published Foil Thickness (mils) 2
damplifier 40sq ft for $115 $2.87 per ft
Published Thickness (mils) 65
Published Foil Thickness (mils) 3
damplifier pro 20sq ft $105 $5.25
Published Thickness (mils) 80
Published Foil Thickness (mils) 4
you can get damplifier which is better product for less.
now keep in mind there is a difference between how thick it is and how much weight it is. you want to mass load and add weight. raamat is cheaper but has 25% more airbubbles so less weight but thicker due to added air.
ALWAYS BUY BUTYL BASED NOT ASPHALT