Whiteout – a large white irregular incurve with loosely curling petals.
US Class 1 Chrysanthemum
 
A classic show bloom, that hold super upright on long strong stems. Grown as a disbud I bet you'd get some knockout flowers but I don't mess with that too much because I'm flower greedy. Someday. Mid to late season. Ours tend to lean a little pink being field grown—temperature plays a big role in mum coloring. With more control, it would be closer to true white. First photo is more open, second still tight in bud, and the last is in an arrangement I entered into the Evergreen Chrysanthemum Association annual show in the Fall.