The American Daffodil Society maintains a "Suggested List of Intermediate-Sized Daffodils".
The ADS defines an intermediate daffodil as a standard daffodil in Divisions 1, 2, 3, 4, or 11 having a single floret whose diameter is typically greater than 50mm and through 80mm.
Intermediate daffodils may be entered in ADS show exibition classes for standard daffodils as well as classes reserved for intermediate daffodils.