How are Lilies measured?
Lilies are measured based on the circumference of the bulb. The greater the circumference of the bulb, the more food can be stored by the plant to give it a better start and greater success.
A larger bulb will produce a fuller plant with more flowers, giving you a more beautiful garden. A 16/18cm Lily will produce 2-3 stems per bulb versus a smaller bulb size.