Are most 60mm diameter exhausts measured from the outside of the pipe or is the inner diameter? If it is the inner diameter, then aftermarket exhausts don't see much bigger than stock exhausts at all. I need to find an exhaust for my crx and I am trying to find a good one. If anyone knows about the inner diameter measurement vs. the outter diameter measurement on certain systems let me know.

 

i think its all from the inside diameter. it might not seem much bigger looking at the diameter, but it you were to figure out the crossectional area, it is quite larger