The Castelli Thermolite 13 Socks live up to the promise of their name. They're thermally insulated socks, but only mildly so, excellent for cool weather riding conditions, and not so insulating as to be uncomfortably warm when the sun comes out or when the pace cranks up. Thermolite is a medium density, hollow core polyester material that promotes breathability and moisture transfer to preserve the comfort of your feet, while still insulating them enough to fend off the chill of fall days. The midfoot is supported by an anatomic band of fabric that prevents cramping and hotspots. The socks have a 13 centimeter cuff, come in the sizes SM, LXL, and XXL, and in the colors Black or White.