I was surprised at the inner pipe diameter, 3"!!! I got this because a shop had it in stock (otherwise its always back ordered for months) and it was only $539 shipped. Plus I recieved it the day after i ordered it. I'll post pics when I install it on Tuesday or Wednseday. I just have to go buy a hi-flow cat first but after that, no more plugged leaky rusty cat and stock exhaust.