In Japan, the Super GT series divides cars into two classes, called GT500 and GT300. These cars are less restricted than their European and American counterparts, with cars often sporting tube frame clips and forced induction kits. Teams are also free to change engines with other models made by the manufacturer. The numbers in the classifications refer to the maximum power (in horsepower) available to each class; this is achieved through the use of engine restrictors. Proponents of the series claim that the Super GT cars are the fastest sports cars in the world, while critics deride the cars as being outside the limits of 'acceptable' modifications. In recent years however, rule changes in both GT500 and GT1 (aimed at eventually allowing both classes to compete with each other in the future) have brought the cars closer to each other, although GT500 cars still have a notable advantage in terms of aerodynamics and cornering performance (enough to compensate for GT1 cars greater power).