Food-grade 304 Stainless Steel Premium Quality, Drink Better Water The interior of SmartKettle is made of integrated 304 stainless steel, which is food grade and free from BPA and other harmful substances. It makes the SmartKettle corrosion-resistant and not easy to rust, so cleaning the inner of the kettle is no longer a difficult problem. With SmartKettle, allowing you to drink safe, odor-free hot water.