How big is a half cup of traditional rice in Japan in Oz?

I see a lot of bowls of rice for sale on the net, but never been to Japan, I know if a traditional size and larger for the American market. I also see different sizes – 8 oz whole way up to 15 ounces in Japan, what is the traditional size, how many ounces it contains, for a bowl of rice?

8.10 oz

[affmage source="ebay" results="90"]Rice Bowl[/affmage]