Pound for pound is a term used in combat sports such as boxing or mixed martial arts to describe a fighter's value in relation to fighters of different weight classes. As these fighters do not compete directly judging the best fighter pound for pound is subjective and ratings vary. They may be based on a range of criteria including "quality of opposition", factors such as how exciting the fighter is or how famous they are, or be an attempt to determine who would win if all those ranked were the same size. In boxing, The Ring magazine maintains a pound for pound rank of fighters. ESPN.com has a list for mixed martial artists.Jose Aldo is an example of a mixed martial arts pound-for-pound top-ranked fighter.