What Our Gearhead(R) Experts Are Saying: "This is my go-to insole for high arches in winter footwear. The merino top keeps feet warm without overheating, and the structured support feels stable all day. The added heel cushioning really helps when you're on hard ground for hours." We turn to the Thermo X High Arch Insole when cold weather calls for dependable warmth and structured support. BootDoc blends its proven 3-Arch Concept with a merino wool top layer, creating an insole that keeps feet comfortable, fresh, and well-supported through winter conditions. The merino top cover naturally regulates temperature and manages moisture, while the rearfoot stabilizer promotes consistent alignment with every step. Extra heel cushioning softens impact on frozen sidewalks and hard surfaces, making this insole a smart choice for winter boots, cold-weather shoes, and long days on your feet.