Cotton has been the traditional filling for futon for many years in Japan but wool is also used in futon for its different properties. Cotton has more natural elasticity so tends to hold its shape better than wool but on the other hand wool has excellent water repellent properties so is often used on top of the cotton futon. Please note that the wool futon we sell cannot be used on their own as they do not have suffiecient padding to be comfortable. They are designed to be used in conjunction with cotton futon and not on their own. On the other hand the cotton futon can be used as they are