The 9 cube ice cube mat is perfect for use with Thermos coolers to keep contents cold. Multiple layers of polyethylene are heat-sealed together to create a strong, insulating bond and each cube contains clear, non-staining purified water. The silver reflective backing provides an extra layer of insulation increasing cold retention. You can store the mat in your freezer until you are ready to use, it will remain flexible when frozen. The cube mat is food safe, reusable and durable.