FeltroBuy Now No lining, no insole, no membrane, no waterproofing: the minimalist Feltro is reduced to the essentials and focuses on pure nature. The mid cut shows what wool can do: The upper material comes from undyed, GOTS certified felt from Spanish brown sheep. The name Feltro means felt in Portuguese. This particularly dense and thick material has a natural temperature regulating effect and keeps feet cozy and warm on cold winter days while preventing