Our 12-oz. BPA-free stainless steel leak-proof insulated food jar keeps food hot or cold for hours! Pack burritos, soup or chilli in the morning, and lunch will be steaming when you are ready to eat. Pack smoothies, chicken salad or yogurt and it stays cool until lunchtime. Cool to the touch when filled with hot foods, and moisture-free when filled with cold foods. Similar to a thermos, our insulated food jar is double-walled and vacuum insulated.Insulated food jars are designed to keep the temperature you start with, so we recommend always pre-heating by pouring very hot water inside and letting sit for a few minutes before pouring out and adding your piping hot food, and pre-chilling in the freezer for a few minutes (lid off) before adding your cold food. Our food jar keeps pre-heated food hot up to 5 hours, and pre-chilled food cold up to 8 hours (and often longer depending on the starting temperature and outside temperature).