i coustom bent everything 2 1/2 diameter but u provide the mufflers yourself oh i can make the piping 3" but will need to have some mods done the the space between the places where the pipes drop down from turbos the frame rails make the pipes stick out too much. if the car is not lowered the bends right there are bout 2" from the ground kinda low i would think 2 1/2" is plenty for me but some people like bigger the better.