Endurance riders usually use a saddle that is designed to be lightweight yet comfortable to horse and rider for long hours of riding. There are saddles designed specifically for endurance riding, though they are not universally used. At the highest levels in FEI, it is usually a variation on the English saddle in shape, although it may have wider panels and stirrups with a wider tread. Lightweight endurance designs based on western saddles are also popular, particularly in AERC rides. Various experimental designs are also common, including treeless and flexible panel saddles. Regardless of design, endurance saddles are very light to ensure the horse does not have to carry unnecessary weight. Many endurance saddles have extra metal rings for the attachment of equipment.