I have no clue. Like I said, I saw the article on belts on Wikipedia (http://en.wikipedia.org/wiki/Karate_belt), it listed 'mon kyu' level belts, I didn't know what it meant. After someone mentioned that they had mon grades in Judo, I looked up just 'mon grade' in relation to karate, and it gave me a page of a karate club that seems to use them. Maybe it's not very widespread, but if that's the case, the Wikipedia article isn't representative of most dojos.