The main goal is noise reduction. At highway speeds, it is 92-93dB in the cab. This is the first time I have done this, but I tried to read up on it. Layer one is this stuff https://www.amazon.com/dp/B07BLSP8JV?psc=1&ref=ppx_yo2ov_dt_b_product_details. It should help deaden sound. Layer 2 will be closed cell foam https://www.amazon.com/dp/B07B75PD8B?psc=1&ref=ppx_yo2ov_dt_b_product_details . It should absorb even more sound. It should also help insulate the cab for heat/cold. My goal is to get a 10dB drop. I am also doing the same inside the doors. I'll probably add some hood insulation and maybe something on the engine side of the firewall as well. A google search and some youtube videos will probably explain in better than I ever could.