Extra Large Diameter - described by AHS as: "A daylily cultivar which has been registered with a bloom size of 7 inches or greater but which is not registered in a specific form category (double, spider, unusual form, polymerous, sculpted) by the hybridizer."
With that description, I have many that have blooms 6.0-6.5 inches and a few that are 7 or more, but most are listed in a specific form category (i.e., Back Scratcher, Lady Neva, Give Me Eight, Ruby Spider, and a few others).
Here are a few that I have that do not have any of the specific forms listed, so maybe these fall into the "Extra Large Diameter" category.
height 25in (64cm), bloom 7in (18.0cm), season EM, Dormant,, Fragrant, Rose self with green throat. (Cherry Festival × Rose Swan)
height 30in (76cm), bloom 7in (18.0cm), season M, Dormant, Tetraploid, Clear candle red self with gold yellow throat.
Thunder and Blazes
height 28in (71cm), bloom 7in (18.0cm), season EE, Rebloom, Evergreen, Tetraploid, Yellow with a wine eyezone and gold edge above a chartreuse throat. ((Celestial Peach × (sdlg × Registration 1998).(D7))) × (Celestial Peach × Registration 1998).(L3)))
height 28in (71cm), bloom 8in (20.5cm), season M, Rebloom, Dormant, Diploid, Pink cream blend with green throat. (Super Valentine × Becky Lynn)
height 26in (66cm), bloom 8.5in (21.5cm), season M, Dormant, Diploid, Fragrant, Rose and cream bitone with cream and orange eyezone and green throat. (Cashmere × (Buff Painted Lady × sdlg))