Mimi
is available in every size between 12.5 and 22.5 mm (inside diameter).
Choose Silver Glossy or Premium Silver for best result and most details.
Please check out your material here:
Shapeways Material Portfolio
If you do not know your ringsize in mm this links may help you:
findmyringsize.com
en.wikipedia.org/wiki/Ring_size
Size at 22.5 mm inside diameter: