I just got a 5" mbrp cat back for my truck. I also ordered the front pipe so that I could switch it out if I ever had to. My question is... I see how the cat back works by undoing the band clamp and putting the flange on the 3 inch to 5 inch reducer. But how does the front pipe connect to the cat back because it just has a 4 inch raw edge. I am at work right now and I was just looking at the parts and I dont see how that works. Maybe I am missing something.

The front pipe is only used if you want to remove the cat.