Pretty sure it's 409 (low-grade stainless steel, designed to get a surface-coating of rust to protect against further corrosion - useless if you want the exhaust to keep the "shine" usually attached to stainless-steel) and 304 (better quality stainless steel, with protection against surface and deep corrosion - better for exhausts, if you want it to last a while and keep that nice reflective shine, but also more expensive to use and harder to work with).

Guess which one a Powerflow franchise used on mine (I only found out afterwards, after discussing with them, when ordering, that the car was going to be going to shows/etc. quite often)!

After 9 months on the car...