TheraPearl Reusable HOT COLD Pack for ANKLE & WRIST Wrap with Strap, Gel Beads New TheraPearl Color Changing Hot + Cold packs feature TheraPearl ColorSmart Technology with pearls that visibly change colors when hot or cold, the pearls turn white when hot and purple when coldReusable hot and cold pack is perfect for lower/upper back pain, torso/midsection injuries, ham/quad pulls, and moreHot and cold compress with gel pearls that conveniently hold temperature for the doctor-recommended time of approximately 20 minutesPlace gel pack in microwave for 45-75 seconds for heat therapy or place in freezer for at least 2 hours for a cold therapeutic pain relief experience, refer to microwave instructions chart