The main specification for bulbs and corms is circumference in cms.
The circumference is defined as "the largest circumference of the bulb, corm or tuber when measured perpendicular to the axis of the stem after having been lifted and air dried."
Standards have been determined, indicating a minimum circumference, and larger grades, which are to be expected in cultivation. It is anticipated that bulbs, corms and rhizomes of these measures would flower in their first season planted in open ground.
The minimum circumference and the grades depend on the species/cvs.