I'm very satisfied
Title says stainless steel, listing says aluminium, not sure what material this is. Either way, it only applies to the ring, as the mask is just transparent plastic that's stuck to the ring. Seems to work OK, although I didn't get nice lines as you'd expect, but just the ends of the lines, making focusing harder. But that might be my lens, and with no clear skies in the near future, I can't really test.