Relief Pak® hot and cold compresses have been used by chiropractors, athletic trainers, physical therapists and massage therapists since the 1980s. Relief-Pak® Cold n' Hot® packs have comfortable soft fabric that conforms to the curves of your skin. Fabric is gentle on the skin, frost-free, and washable. Hot and Cold packs are also available with a urethane covering providing extended durability for high volume chiropractic offices. 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.