C Group bipolar spots of wich one of the principal spots is surrounded by penumbra . There is no upper limit to the lenght of the group. D Bipolar group whose principal spots have penumbra. In general the lenght of the group is lower than 10 degrees of heliographic lognitude. It has a complex structure.
Many smaller spots are between the principal spots.
The lenght of the group is at least equal to 10 degrees of heliographic lognitude. G Great bipolar group without small spot enters the two principal spots. The lenght of the group is minimum 10 degrees. H Unipolar spot with half-light. The diameter is higher than 2.5 degrees.