[citation needed] The two best studied compact toroids are the spheromak and field-reversed configuration (FRC).
The two examplar types; Field-reversed configuration plasma with a null toroid, firstly, is generally produced by prolate-theta-pinches with the necessarily existing field condition where the field magnetic bias is in a reversed situation.
The FRC is also toroidal, but extended into a tubular shape or hollow cylinder.
The main difference between the two is that the spheromak contains poloidal (vertical rings) and toroidal (horizontal) magnetic fields, while the FRC has only the poloidal fields and requires an external magnet for confinement.
However, the spheromak had generated better confinement times and temperatures, and recent work suggests that great advances in performance can be made.