These are listed in whole sizes but they are tagged differently. The size 9 is tagged  "9 / 9.5".  These are very strangely proportioned.  The width looks and feels like a normal "medium" or "B" width shoe, but they taper toward the heal and the point where the straps enter the base is so narrow that they are under your foot rather than at the sides. Making these miserably uncomfortable to wear for any length of time.

I have several pairs of Vionic Bella II flip flops, and they tend to run too long and too wide, so I need a whole size smaller, I wear a size 8 in those.

The Noosa also seem a little long for a true size 9, but they are so narrow in this size, that an 8 would be way too narrow.

They get 2 stars for arch support and color.  Really disappointed that these do not fit better.