These rubber boots are made of the finest single-estate natural rubber and harvested sustainably. The rubber is mixed with our own secret recipe making the fundamental composition 80% pure, natural rubber and 20% secret recipe. Entirely PVC-free, our boots contain no animal by-products. The result is a sturdy and reliable companion for rainy days. The zipper on the inside of the boot shaft is water repellent. You can wear our rubber boots even on the coldest days without having to worry about the cold ruining them ? we have chosen the best materials that can withstand temperatures down to -20 degrees Celsius. Natural rubber will eventually develop a white surface over the years if you do not treat it regularly. This is simply because the rubber loses its essential oil. To keep your boots in great condition for many years to come, we recommend that you treat them with our oil once a month.