Originally Posted by SouthArk370Z

I got the GTMat free sample (don't know if it's still available or not). It was rather thin (30-35 mil, IIRC), which made it easy to form. It wasn't too tacky - as long as I hadn't rolled it down I could easily peel it off to relocate. Sound reduction was noticeable - quite an accomplishment considering this was my first install, I didn't have enough to completely cover the shock towers, and it was free (even came with a small roller; all I had to supply was some scissors and labor). If I were to do it again, I'd go with thicker material (50-70 mil sounds about right) and make sure I got enough to cover the shock towers (or start there and leave something else uncovered).
And I'd go with the smaller, pre-cut squares. The free sample was a 3'x3' sheet which was unwieldy at first.

I've never used DynaMat, so can't compare the two. Going by the comments on this site, the GTMat stuff is of the same general quality as DynaMat and less expensive. Most ppl are reporting that service at GTMat is exemplary. I'll be using more GTMat when I do the areas I missed when the free sample ran out.

Edit: Apparently the sample was 50 mil. I'd go with the 70-80 mil stuff.

Originally Posted by GTMat

The free sample was for the 50mil Pro material. Our Ultra is rated at 80mil and our Onyx at 70mil. Remember, Pro and Ultra work just as well as the leading name brand but are discounted due to the asphalt based composition. It is definitely the best way to go when on a budget. The Onyx version is the exact same material as that leading brand but we are able to price it cheaper.