The (M) run narrow! If you have a wide foot I would not recommend this width. If they have a width size that you can choose I would highly recommend doing that. I have a very narrow foot and these fit perfectly. If you are looking for a super comfy light weight sandal for the Summer you have found it. I am almost tempted to get another pair for future wears. Companies tend to discontinue my favorite styles. LOVE THESE SANDALS! No worries on getting these wet so it is a bonus!

Thank you Birkenstock!