The hatinator bases seen above are worn on a headband. A hatinator is a hybrid of a hat & fascinator. Typically a hatinator "base" will have a shallow crown, hence the reason for a headband to securely keep it on your head.
Brim sizes per hat base:
Harlyn:
UM7:
UXXL24:
UXXL2:
UXXL16:
Henley: 18.25"
Jan: 19.5"
Oprah: 20
Wide-side:
UXL1:
UXXL15:
Harlyn: