Long praised in Japan, Aomori Hiba is a slow-growing, long lived cypress tree whose wood has been used in the construction of temples and notable buildings throughout Japan for centuries. Hiba wood is naturally an antiseptic, water-resistant, insect-repelling, and a calming aromatic. Cul de Sac has developed a way to vapor extract the essential oil used in their products from waste lumber harvested from 250 year-old trees, thus recycling this useful and pleasing material. Pack of 2 shoe inserts made of undried Hiba wood. Replace shoe inserts every 3-6 months.