The 20 oz tumbler is Made from double wall high quality 304 18/8 grade stainless steel which won¡¯t alter flavors or leach chemicals.This durable tumbler can effectively prevent rust though electro-polishing.Lead free and durable.With double-wall vacuum insulation technology,which can retain the temperature of your chosen beverage for a prolonged period of time. Enjoy Beverage Cold or Hot. Under normal temperature, Any hot drinks can keep hot for up to 6 hours and cold drinks can keep cold.