This design is available in copper and brass.
Approximately 2-1/2" diameter.
This item comes with two sets of twelve rings, bundled together by a ribbon. These are hammered out by hand, so they have a rustic look to them. To wear them, remove the ribbon; each individual ring has a slit so you can put them through your ear.
To wear all twelve ring in each ear (or through eyelets of some sort), you should probably be at least 7/16", although any larger size could wear these without fear of them falling out. Additionally, smaller sizes could wear these through eyelets, you just wouldn't be able to put all twelve rings in.