Compact toroids are a class of toroidal plasma configurations that are self-stable, and whose configuration does not require magnet coils running through the center of the toroid. They are studied primarily in the field of fusion energy, where the lack of complex magnets and a simple geometry may allow the construction of dramatically simpler and less expensive fusion reactors. The two best studied compact toroids are the spheromak and field-reversed configuration (FRC). A third configuration, the particle ring, does not appear to have attractive performance.