World Centric bowls are made from wheat straw, a leftover agricultural fiber and an annually renewable resource. Microwave and freezer safe, can be used for both hot and cold items. No plastic or wax lining. Suitable for hot foods up to 220 deg F. Conform to FDA approved for food use. Gluten-free. Wheatstraw is the remaining plant fiber after the grain (which stores the proteins and allergens) has been removed.