If between sizes, we generally recommend choosing the smaller size. However, everyone's feet are different and the way the amount of support felt can be different depending on the shoe they are placed in. A shoe with a narrower midfoot section, some existing support and a more rigid medial wall will cause the Soul Insole to feel much higher in the arch region than a flat, wide shoe with a soft medial wall. For your first pair, we suggest trying the smaller size. If you feel like you need even more support, next time try the next size up.