The uppers of these Firestalker Wildland boots are made with black oil-tanned fire leather. Oil-tanned leather is super soft and flexible. More importantly, the uppers of these Thorogood boots are water-, stain-, damage-, flame- and cut-resistant. Inside, you'll find Cambrelle lining, a non-woven fabric that is super durable and abrasion-resistant. Fire fighting means heat and sweat, but this lining keeps feet cooler and can hold up to 350% of its own dry weight before feeling wet. Also, Cambrelle lining inhibits odor and minimizes stains and the growth of mildew when you wear these FR boots. Cambrelle carries the American Podiatric Medical Association seal of approval. Material: Leather.