The Thinkbaby Bento Box is comprised of stainless steel wrapped in polypropylene for durability and easy cleaning, and is free from harmful chemicals like BPA, phthalates, melamine, and PET. The easy-to-clasp lid creates an air-tight seal, but can still be easily opened by children. Perfect as a lunch or snack box. It is dishwasher-safe, and we recommend placing in the top rack.