Yes some of the rings are not perfectly round. No they are not polished. They do, in fact, clatter
like a shopping cart hitting a lamp post.
However, they are priced in appropriately and I
can use them at the fairgrounds or a children's show and not worry about them taking some abuse.
For what they are they are lovely.
Now the answer to the $3000 question: 3cm. You're
welcome.