The pad eyes and biners in this set are fine. I will, however, be replacing the turnbuckles. All 4 tried to crossthread when I was attempting to tension my sail. I got them tight enough, but I would feel better with something sturdier. One of the comments says they are M5 size. I can find a set of M8 size turnbuckles for about the price of this set, which is probably what I will go with.
Overall, the set is fine. It seems to actually be stainless steel, which is definitely what you want. Maybe my sail is just too big for it, though, because the turnbuckles seem lacking.