Instep: very open instep area, so fitting for high or lower instep is not a factor.

Arch: Super cushion soles, various arches should be able to comfortable fit this shoe.

Width: Smaller widths may feel the need to size down or adjust the buckles accordingly for a more snug fit.

Length: This is what plays the biggest part in overall size.  Going up a size will increase the length of the shoe.

If you are a 1/2 size, size down. 

Black straps, White soles, and a cute patterned sole.