http://www.potsaa.com/rice-bowl/

What is the average size of a traditional bowl of rice to Japan in Oz?
I see a lot of rice bowls for sale on the net, but having never been to Japan, I do not know if they are of traditional size or is greater for the U.S. market. I also see different sizes – From 8 oz all the way to 15 ounces in Japan, what is the traditional size, how many ounces it contains, for a bowl of rice?
8-10 oz
How to Make Gyudon (Japanese Beef Rice Bowl)