I installed double glazing on my Dodge Dakota but it was too loud. Previously I installed an internal (in the exhaust pipe) coil muffler. It did a good job of blocking out noise, but it was limiting and ended up being blown out of the pipe. I bought it even though the information was minimal. The entrance is 4 inches, the exit is also 4 inches, but the exit is curved inwards. I had to make an adapter to attach it to my 3" pipe. The product image shows the intake side. The muffler seems to ventβ¦