I tried these on in a brick-and-mortar store for fit. They run a half size smaller in many cases so I got a half size larger. Very comfortable with socks. Without socks, your feet will need to become accustomed to the plastic-like feeling of the foot bed. My feel need to toughen up a bit as they feel tender after a few hours barefoot in the shoe. So as not to slip off easily, inserting your foot is snug so I use the loop in the back to pull them.