Inner and Outer side of mug is made from 304 Grade Steel which is Rust Free and 100% Food Grade and BPA Free. Flip lid is easy to use with a straw or drink directly and silicon seal for spill proof. The mug comes with unique poem/rhymes design for your kids or a special gift for your little loved ones. Best Usage: Great for all kinds of hot and cold beverages like milk, coffee, tea, juice etc.