Highly recommended. One of the most audible, passive sound treatments one can apply. Before the treatment, I had to turn the bass from my door speakers all the way down and it still made that sort of bass 'farting' sound between the panels. In my case, I could tap on the exterior panels with my fingertips and could sense that another layer would help suppress that 'tinny' sound. You can hear it resonate to the point of almost ringing. The other tell tale if sound deadening would work is, when closing the doors. The difference perhaps, between *crash* sound or a more solid sound that leans more towards a "thud" sound. \n\nNoico is the brand I used and it is 80mils thick and the kit I got was heavy in the box. It was more than enough to do 2 doors, on the inside of the exterior panel, and on the metal that the upholstered panel covers attach to. I also sound deadened behind the walls and rear speakers of my xtracab portion of the truck. There are plastic inserts that house the speakers and they even benefitted from the treatment. Took me about 5 hrs at a casual pace, including washing\/drying all surfaces. \n\nNext will be adding the amps (already have these items) and subwoofer but this made enough of a difference that I could have done without for awhile. I was able to add a reasonable amount of bass, and it plays clearer, with the ability to play it much louder than before. Louder in the way of headroom, in my case, because it now plays much clearer in the range I generally listen at.