Its a bit of a bad picture indeed, could find a better one.
About the size: they come in various sizes, but in general are about and inch in diameter. Also, its made mostly from metal, not rubber or filter material.
OK -- as the others have said, "it could be anything" -- Even a piece of scrap.
My last guess is --- ready???? It's a nipple ring used for enhancement or medical corrections.
A circle within a circle opens the entire universe for answers and in infinity, all wrong.
I found that site while just looking at images of various things to post as objects. It looks like they would sell anything and you probably will end up with a package that you don't want.