These fit loosely, and by keeping a warm air pocket around your feet, keep your feet very warm at night. My daughter describes them as "like wearing the feet from footie pajamas." They have thin treads on the bottom, so they are non-slip when you get up, and they are thin enough to slip inside a slipper if you wish to. They also have large enough calf-openings to fit larger people, which most fleece socks dont. I've had other fleece socks, but these are by far the best!