In my experience, it makes the truck a lot more comfortable regardless of the speed you travel. Dynamat is the best brand, but you can use some of the other brands which are quite a bit cheaper with very good results. The name of the brand I am currently using escapes me. I will look at it in the near future & post it.
Bill
The name of the brand I am using currently is FatMat, it is a little thinner than Dynamat but it is a lot less expensive. It was available on Ebay when I bought mine. There is a difference after installing it.
