Medium pronation, it's a natural fit. Love this shoe! I bought the GTS 10 and had to have this one. Brooks has been my favorite shoe for over 30 years!! Very consistent product. Stable feel, comfy hug , not overly tight in the toe area. I wear a 7 1/2 B, bought this in an 8 B. I like that the purple makes the shoe look darker so it doesn't appear dirty right away.