Thoroughbred horse racing normally is limited to 2-5-year-old horses. Races are conducted over flat, oval tracks at distances from five to 12 furlong. A furlong is 1/8 mile (0.2 km). Thoroughbreds are a breed of horse developed for speed and elegance. Some also are used for hunting and polo. The breed is about 16 hands (64 inches or 1.6 meters) tall and usually weighs between 1,000-1,500 pounds (455-680 kg). All thoroughbreds descend from three stallions: Godolphin Barb, Darley Arabian, and Bylerly Turk. They were imported from England between 1689-1724.