I wear 10.5C in Allen Edmonds 5 last which according to the Swims size chart says I should wear size XL. They fit very loose, I ended up changing them to size L and they fit PERFECTLY. I wear them through the wet and snowy midwest fall and winter and they do a great job of holding the leather soles on my dress shoes. . I considered carrying them the three-block walk from the office parking lot to the office almost every day to protect them from the wear and tear of the concrete.