The answer is actually quite simple. If you normally have a hard time finding the right width shoe because your foot is either too narrow or too wide, then you might consider going with either a narrow, or a wide fit, depending on whether your foot is too narrow or too wide for shoes. Otherwise, we recommend going with a “medium”. Since we manufacture these shoes ourselves from scratch, we have made this option available to help those that tend to have problems finding a shoe source where they can order shoes with these custom modifications.