The hot-water bottle

Do you know the hot-water bottle. It is said yutanpo in Japan. This is a bottle made of the metal or the pottery. The use is to pour the hot water and to cover the cloth because of prevention of the burn. This start to be popular secretly in Japan. This cause is to jump the price of the oil. The oil stove is used ingeneral in Japan. But this change is good for the earth. This chage is green. I want to ingrain this change.