Sports car racing is a form of motorsport road racing which utilises sports cars that have two seats and enclosed wheels. They may be purpose-built prototypes or grand tourers based on road-going models. Sports car racing is one of the main types of circuit auto racing, alongside open-wheel racing, touring car racing and stock car racing. Sports car races are often, though not always, endurance races that are run over particularly long distances or large amounts of time, resulting in a larger emphasis on the reliability and efficiency of the car and its drivers as opposed to outright car performance or driver skills. The FIA World Endurance Championship is an example of one of the best known sports car racing series.