these provide the most freedom over fences. Although a standing martingale (a strap connecting directly to the horse's noseband) is commonly seen on show hunters and may be helpful in keeping a horse from throwing its head up, it also may be quite dangerous in the event of a stumble, restricting a horse from using its head to regain its balance. For this reason, standing martingales are not used in show jumping or eventing. Breastplates also are common, used to keep the saddle in place as the horse goes over large fences. Rider attire Rider attire may be somewhat less formal than that used in hunter riding. An approved ASTM/SEI equestrian helmet with a harness is always required, however, and is a practical necessity to protect the rider's head in the event of a fall. Tall boots are required, usually black. Spurs are optional, but commonly used. Breeches are traditional in color, usually white, tan, or beige. At approved competitions, depending on sanctioning organization, a dark-colored coat usually is worn (although under the rules of the USEF tweed or wash jackets are allowed in the summer and lighter colors are currently in fashion), with a light-colored (usually white) ratcatcher-style shirt and either a choker or stock tie. In hot summer weather, many riders wear a simple short-sleeved "polo" style shirt with helmet, boots and breeches, and even where coats are required, the judges may waive the coat rule in extremely hot weather. Gloves, usually black, are optional, as is the plaiting of the horse's mane and tail. At FEI Grand Prix levels, dress is more strictly controlled. Riders must wear white or light-colored shirts, white ties or chokers, black or brown boots, white or light fawn breeches, and red or black jackets. Members of the military, police forces, and national studs, however, retain the right to wear their service uniforms instead of FEI-prescribed dress. In some circumstances, members of international teams may wear jackets in their country's respective colors or add national insignia. Types of competition Grand Prix: the highest level of show jumping. Run under International Federation for Equestrian Sports (FEI) rules, the horse jumps a course of 10 to 16 obstacles, with heights up to and spreads of up to . Grand Prix-level show jumping competitions include the Olympics, the World Equestrian Games, and other series of internationally ranked events. Grand Prix show jumping is normally referred to