Food grade stainless steel material, easy to clean, not easy to rust. You can take this kids to school, travel, outdoor picnic. This stainless steel 's design by by the design of japanese lunchbox, perfect for student and office workers. The bento box is portable and doesn't take up space in a freezer safe, you can make your kids more appetite for lunch, it's the perfect bento box for kids. This thermal insulation bento has a sturdy design for serving food.