​The M or Marblehead Class, sometimes called the "50/800", is a medium size high performance development class. It's original concept in the 1930's was to produce the largest model that would conveniently fit in the standard American car of the time. The class is a development class with the main restrictions being a hull length of 50 inches and a sail area of 800 square inches. The class has been highly developed over the years to produce a high performance model that can be sailed in a wide range of conditions, assuming the owner has the appropriate rigs. Today's M weighs around ten pounds and carries an 85 inch rig in most conditions. The hull and rigs tend to use advanced materials and techniques. Boats are available from several suppliers who can provide them from basic kit form to fully assembled. There is also an active used boat market at the local level.

The M Class has a large base, with over four hundred competitive models in existence. It is sailed in most areas of the country. Competition is available from club level to national level, and even international level. As an international class with the same rule as the rest of the world (except the measurements for AMYA are in inches and pounds), AMYA members can attend regattas abroad. They can also take advantage of several excellent foreign suppliers.

When you are looking for a class to enter, look at the M Class. It has much to offer.