I get this ring from a company called Bright. See below for the description of what its made of.
Face Width: 14 mm
Band Width: 2 mm
Finish: Black IP; High Polish
316L is the highest grade of stainless steel used in the jewelry market. It is so good at resisting fade, rust, and corrosion, that it is used in architecture as well as in marine environments. At the same time, it is safe to use for medical purposes inside the body. For this reason the stainless steel rings we carry are made with this same grade of steel. It will not fade, change color, or leave stains on your body. It doesn’t even require any maintenance to keep it looking new.