Combine class ratings are determined, as far as i know, by four factors. Grain bin size, horsepower, threshing area and cleaning area. Hence having an oversized grain bin wont get your combine in a higher class, nor will a smaller tank drop you to a lower a class. All factors are considered and a "score" arrived at that places a machine, whether green, red, silver or yellow in a class. The class rating is NOT determined by the company, this is done by an independent non-biased group.( Eliminates, for example, JD from saying ' our 9600 is a class 4 !!!! lol )To the best of my knowledge glass 7 is the largest at the moment.