XS and SSAC are identical & from the same company (kinda like ZZP/Stattama/EasyPerformance). You can actually click on the bottom of the SSAutoChrome.com website & go to XSPower, which seems to be their label on a couple turbo exhaust manifolds.
Since day one from buying the 1st set of these headers 3+yrs ago, they've been said to be 321. Personally, as long as they were a 300 grade, I was happy.
I've even made comments to the SSAC site, asking them to fix their descriptions, since some lazy marketing person copy-pasted PaceSetter info, leading onlookers to think SSAC's are made with inferior material than stainless. So it doesn't surprise me that eBay listing descriptions are goobered up as well.
- Dave
