To use, fold the PackIt Freezable Lunch bag flat and store it in the freezer overnight (12 hours). In the morning, the walls of the lunch bag will be completely frozen and ready to chill items for hours. PackIt's reusable Lunch Bags chill food all day, letting you pack healthy foods that would spoil in other bags such as: yogurt, deli meat, milk, fruits and veggies. The cooling power lasts long enough to bring home leftovers, which reduces waste and saves you money. PackIt's Freezable Lunch Bag is the original bag with built-in cooling that keeps anything you pack cooler, longer. The secret is PackIt's patented cooling technology. Freezable gel is permanently built into the lunch bag so you will never need to buy separate freezable ice packs or gel packs again!