What does SSTL stand for?

Stainless Steel

Good corrosion resistance due to a high chromium content is the key characteristic. Opinions vary on the level of chromium (Cr) at which a steel becomes stainless, but it is at least 10.5%. Nickel (Ni) and molybdenum (Mo) are often present, and manganese, copper, titanium, silicon + other alloying elements may be added. The principal grades are austenitic (typically 16-26% Cr, 6-22 Ni); ferritic (10.5-28% Cr with no/low Ni); martensitic (higher carbon content than ferritic and typically 12-19% Cr with low/no Ni); and duplex, a dual-phase austenitic/ferritic steel (Cr>21%, Ni<8%).