Thermal insulating balls with bag, perfect to fit all sizes of containers. Up to 90% reduction in evaporation, water and heat loss when cooking with a thermal flask. Reduced energy loss during sous vide cooking due to surface charge between water and air. Increased temperature accuracy of your Roner immersion simmer. Reduced risk of burns due to floating insulating balls. Hollow, insulated spheres allow hours of cooking without adding water. BPA-free, FDA.