If the cigar is not a cylinder, the ring gauge shown is generally the bigger one. Churchill, Robusto, Corona, Panatela, etc., but these are not strict definitions. Each one is in a range of length and diameter. Cigar strength igars are classified as mild, medium, or full bodied. The body refers to the impact the smoke is supposed to have inside the mouth.
Cigar makers know what type of tobaccos they have to use to achieve the desired level of impact.
The difficulty lies in blending them to get a pleasant balance between taste and aroma.