Per Bergvall Dec 14, 2009:

JI-klassen er ikke bare 8-metersklassen Following the regattas in the bay of Cannes was impossible because of the distance but in the late afternoon when the yachts were back in the harbour, crews ranging sails and cleaning up, lot of amateurs assembled at the quay Saint-Pierre and quai Laubeuf on the west part of the Vieux-Port to admire the sailing boats called the 6 Meter Class, 8 Meter Class and 12 Meter class.
These yachts were designed uniquely to race. The rating rule was created in 1906 in London, that's probably why the class name in meters does not actually represent the length of the boat, which is based on a complicated mathematical equation. Actually the 6M JI class has a total length of 11 m, the 8M JI has a total length of 14 m and the 12 M JI class is 20 m long (this is the America’s Cup class).