First, I am Women's 8.5 (US) shoe size and the Small just fit. I have checked the section on here that says "Runs small" because the size chart says that the small should fit up to a men's 8 and it most certainly would not. If your foot is larger than that the small will not fit. I wanted to love these, but they felt like a $20 slipper. There is no support, which I wasn't necessarily expecting, but they felt sloppy, almost like it was hard to keep the bottom of the slipper from shifting out to the side. But my main issue was that the stitching that goes across the top of your foot/ankle junction (at the 90ish degree bend) dug into me. There should be some sort of soft band or something else there at this price point. They weren't tight on me. They actually fit nicely, but just lounging around my feet would start to get fatigued and sore from that part . After giving them a chance for a solid weekend of lounging, they are getting returned.