Like I keep saying, this is an extremely easy job. The instructions are clear and the assembly is really straightforward-which is great if you're a wannabe fabricator like I am. Assembly begins by determining the outlet end of the main core tube and readying the smallest (in this case the 3-inch) ring for placement on it. Car Chemistry marks the inlet and outlet sides of the core tube so pay attention and make sure you begin on the inlet side of the tube. The first disc is pressed or driven onto the core tube (a section of 2 1/4-inch pipe works great) downward toward the bottom of the tube.