The One Metre class is the newest and probably the most popular. There are limits on the construction materials, ballast weight and overall length. The rules are complicated but it does control the costs and enables the home builder to construct a competitive yacht.
There are three permitted sail rigs which have their dimensions tightly controlled.This is a very popular class and has a large international following. It can be easily transported, the maximum length is one metre and four kg. is the minimum weight.
The International One Metre class rules are here.