Can be heated in microwave or cooled in freezer. Beads keep pack flexible when cold. Instructions are printed on the back. Aqua Pearls™ are soft, smooth, easy to use & conform to your body. Instructions are imprinted on item. Microwave & freezer safe. Store in refrigerator or freezer for cool use. Microwave for use as hot pack. Safety tested for CPSIA, FDA and TRA (Toxicological Risk Assessment). Reusable, pliable & non-toxic. Complies with CPSIA, FDA. You can customized different sizes and designs. Random sample is available for check quality.