My a solute favorite sandals! I received compliments where ever I went! If I tied them tight enough they stayed up. Generally a couple hours of wearing them they'd start sliding down, you can feel when they are starting to get loose and slide down though, so untying the back and tying them up again tighter is easy. Not exactly sure how to describe the material of the strings. Faux suede, but whatever they are, they aren't a normal string so it helps keep them up. Tying them tight ensures they stay up, but they can dig into the skin a little bit. They are worth it to me! I ordered a 6.5, they fit great. I'm generally a 6-6.5. I could have ordered the 6, but 6.5 fits good. These are so versatile and go with anything. I ordered this in the taupe. I'll be ordering more colors. Hope this review helps!