There are three types of Quarter Horses: stock, halter, and racing type. Compared to other types, the racing type is leaner, lighter, has finer bone in the legs, and is sleeker. They have similar appearance as Thoroughbreds. The stock type is muscular with good bone, has a short back, deep body, and full neck. They are smaller and quicker, somewhat stockier but agile. They are commonly used for Western-style riding and cattle-handling. The halter types are also known as the bulldog Quarter horse. They are the biggest of them all, very muscular and heavy. They have massive muscles and shoulders. Hind quarters are large and the body has substantial barrel.
All three types have strong, sturdy legs with good bone and a natural gaits. However, the racing type is the most graceful of the three. The stock type is the most functional and also the most popular, and the halter/bulldog type is the strongest.