THERMAL RESEARCH AND DEVELOPMENT! There is no comparison to sound and quality. have not dynoed to see but i felt the difference around a certain rpm range with this lovely exhaust. i got mine a few years ago brand new shipped for $480 and it is still blingin to this day. get it you will love it with no regrets at all! i think the pipe size is 2 1\4 mandrel bent stainless steel. ok got to stop cause i can go on and on about this exhaust that is pure sex, and quite frankly i think i am starting to get a bit excited