The main class regulation is a restriction on a single quantity output from a formula involving the boat's rating length L, weight (expressed as a displacement D) and sail area S; the regulation states that the output of this formula must not exceed 5.500 metres.
There is considerable scope for variations in design while still meeting this restriction, and as a result each 5.5 metre boat is unique.
It achieved a position as the smallest new international metre class and some hundreds boats were built.
5.5 metre boats replaced the International 6-metre at the 1956 Olympic Games held in Melbourne, Australia.
[9] Since the development of the class spanned more than half a century the early boats are not competitive to race against the modern designs.