Seed Sd922 Vacuum Fresh-keeping Leak-proof Food Warmer 304 Stainless-steel Lunch Jar,coffee Keep Fresh:Easy to extract the air with vacuum pump to extend the refreshing time of food. Put the pump on the middle hole of the cap,and then use Vacuum stick to extract air several times. Heat-resistant:Container is adopted Ceramics PTC heating frame,it can be bear high temperature and keep color for a long lifetime. Safety:It is constant temperature heating,which can adjust power automatically.