Features: The inner layer using highquality stainless steel material, mirrorpolished and easy to clean.The outer layer uses food grade PP material, high temperature resistant, safe and hygienic. Upgraded Lunch Box: Concealed doublecurved handle is small and portable, suitable for home, work, travel, and school. The airpermeable sealing valve can eliminate air, so that the food in the box is better sealed, and convenient to open the lid. Keep Warm: The builtin sealing rubber ring improves the sealing performance of the lunch box and keeps heat preservation lasting. Safe to Use: Non-toxic, health and safety. Safety lock design, adopts PP plastic, which can be fastened with one click to prevent leakage. There are 3 size for you to choose, you can choose according to your demands. Practical: Easy to clean, practical, low maintenance and environmentally friendly.Our lunch box can keep the food warm 3-4 hours (but varies depending on your local station, the weather and temperature, the exact time cannot reach this keep the heating time)