As advertised, they do appear to be 304 stainless; no corrosion at all, even in our damp Oregon weather. The spacing is also a little tighter than most others, which makes them nicer to cook on. (Most of the reason people go for 8mm rods, I think, is to get tighter spacing, not because they're all that more durable than a 7mm rod.) They were also the only ones (at the time) that matched the length of the OEM Weber grates, which means they fit better even if the cookbox is a little bowed.
I went through the same process of choosing that you're going through, and these were overall the very best value. I'd buy them again.