What size pipe to buy?

[KCz Eclipse]

Alright, this is a pretty simple thread. I dont want to buy a pre made test pipe because chances are that the flanges on my catback and dp match up isnt very good. So i want to buy a foot and a half piece of stainless and some flanges and have a shop make one thatll fit. So i know to buy 3 inch pipe but the thickness of the pipe i dont know what to choose. I dont want to buy something to thick or thin. Let me know.

Thanks

Anyone?

 

[KCz Eclipse]

all i am looking for is a thickness