Yeh he's confused, whatever you get look at these things:
Titanium for lightness but costs more,
Stainless steel next and won't rust
Normal steel for cheapness
3 inch turbo back is the norm
Resonator so you don't get drone
High flow cat good
Loud or quiet up to you and end muffler size
O2 sensor mounts pending your states legislation

I have a store made turbo back SS with high flow cat resonator and quiet muffler that is about as loud as a motorbike, I also have o2 mounts.
The car came with it
But if I was going to buy one now it would Ti with the same specs just to save some weight