For the cost-conscious consumer, the new Basic Comfort CorPaks are filled with the same temperature-retaining fill as our other CorPaks, but have a cost-saving plastic covering instead of fabric. Relief from strains, sprains, tendonitis and other injuries. Because all CorPaks have more temperature-retaining fill content than other hot and cold packs, they retain temperatures longer. Non-toxic mud is biodegradable. Basic Comfort CorPaks should be used with a towel or other protective covering. Store in the freezer; stays soft and pliable. Heat in microwave.