Footwear products incorporating the use of natural materials; therein, and, more particularly, insoles, liners, and footwear incorporating sisal material. The sisal material is arranged so as to provide direct contact with a user foot in order to avail to the user foot the sisal therapeutic benefits...http://www.google.co.uk/patents/US5992055?utm_source=gb-gplus-sharePatent US5992055 - Insoles, liners and footwear incorporating sisal material
