The Relief-Pak Cold n' Hot Compress has a comfortable soft fabric that conforms to the curves of your skin. Fabric is gentle on the skin, frost-free, and washable. Put the pack in microwave or chill in freezer. When heated, soothes discomfort from stiff neck, backache, arthritis, sprains and bruises. When chilled, soothes discomfort from injury, sprains and strains, muscle soreness, bruises, swelling and tension headaches. The non-toxic, non-crystallizing gel allows pack to contour and stay pliable when heated or chilled. The pack can be used with standard Velcro hook to hold pack in place.