international racing trophy for sailing yachts of about one-ton displacement. From 1907 to 1955 the cup was the object of a major competition for 20-foot (6-metre) yachts, but with the decline of that class the cup was put up for challenge in 1965 by the Cercle de la Voile de Paris, a French yacht club, for boats rated up to 22 feet (7 m) by the measurement formula of the Royal Ocean Racing Club of Great Britain. Competing nations could enter up to three yachts each, with the winning yacht determined by performance in a series of races. In the early years, there were three challenges consisting of three races, the first and third of 30 miles (48 km) around a closed course and a second, counting double, a distance race of up to 300 miles (500 km), run without handicap. In 1968 two more short races were added. A new rating of 27.5 feet (8.4 m), by rules of the International Yacht Racing Union, was adopted for the 1971 event and reaffirmed by the Offshore Racing Council in 1978.