For therapeutic relief of muscle aches or pains. Maintains an even temperature over the entire pack. Leaf-proof and contains no liquids or dyes. Biodegradable and contains only non-toxic ingredients. Versatile freezer or microwave. Remains soft and pliable. From freezer to microwave and from microwave to freezer. Designed for 25 seconds in microwave. Latex free. Remains flexible after freezing. Cleans easily with soap and water. One side insulation.