We watch our weight! Fabric weight, that is. Ultralight, light, medium, heavy and extra heavy, the type of padding and insulation you’ll need in a sock varies depending on your activity. Fabric weight describes the warmth and padding level of a sock. Skinny knits are best when you need a close fit, while thicker fabrics provide excellent cushion and insulation. A heavy cushion sock is best if you’re on your feet all day while an ultralight sock will minimize blistering if running is your thing.