The International One Metre (IOM) is a class of Radio Sailing Boat used for racing under the World Sailing - Racing Rules of Sailing. It is a measurement-controlled box rule originally created by the ISAF-RSD (now the International Radio Sailing Association) in 1988 in an attempt to harmonise the various one metre rules created around the world. The IOM Class Rules specify a standardised sail plan and control of the other major performance dimensions (displacement, length, and draught) while allowing some freedom in hull design. The IOM is now the largest and arguably most competitive of all radio sailing classes.