I've had a pair of these sandals for a couple of years, and they are extremely comfortable. I decided to order a new pair in a different color to take on a trip that will involve a lot of walking, so ordered exactly the same size, but was really disappointed that this pair was quite a bit wider.  I found them hard to keep on my feet, so I have returned them.  I wondered if they were mis-marked. Instead of being 8M, perhaps they were 8W?