Bundgaard Sailor Warm Rubber Boot in navy. From Pedterra: Bundgaard Warm Sailor boots are a great minimalist friendly waterproof boot option for those snowy, wet and cold days. These rubber boots are lined with 40% wool and 60% Dacron to help keep your child’s toes warm and cozy. The boot comes with a wide fit with room for growth and space for toes to wiggle. Bundgaard Sailor Boots boots are suitable for temperatures as low as 5 degrees Fahrenheit, but if you pair with a wool sock you can make them even warmer!