Sixes are a construction class, meaning that the boats are not identical but are all designed to meet specific measurement formula, in this case International rule.

The International rule was set up in 1907 to replace numerous handicap systems which were often local, or at best national, and often also fairly simple, producing extreme boats which were fast but lightly constructed and impractical.

The 1920s and '30s were 'golden age' of the International Rule boats and Sixes were still the most popular class, attracting top sailors and designers to compete for prestigious trophies such as Scandinavian Gold Cup and Olympic medals.

The Class has undergone a renaissance which has continued to this day, with many old yachts restored or rebuilt to racing condition.

In 2019 the International Six Metre Association launched an online archive website, allowing researchers around the world to access historical information about the class.