304L (18/8) Antibacterial Stainless Steel, non-toxic, corrosion resistant, antibacterial. Lab results show 99% resistant to Staphylococcus aureus and Escherichia coli. Comes with silicone lid, excellent leak-proof seal. High rim is designed to prevent child’s mouth to come in contact with plastic outer sleeve. Removable Non-toxic PP Outer Sleeve, PP outer sleeve layer is a safety feature that protects babies from high heat. The Stainless steel can be heated directly, when PP outer sleeve is removed. Food Grade Silicone Lid, keep food safe and fresh.