Back Gel Ice Pack Wrap: Pain Relief Heat Pad for Hot & Cold Therapy on Large Body Parts (Upper & Lower Back, Torso, Shoulder, Lumbar, Hip, and Waist) | Adjustable, Flexible, Microwaveable & Reusable Flatten the back wrap in the microwave. Heat one side for 30 seconds only*. Store the back wrap in the freezer for at least 2 hours*. Check the temperature. If it is too cold, wrap a towel around it before applying it on your body. (In cases of severeinjury, wet the towel prior to application for greater cold penetration.)  <span class="a-text-italic">*The back wrap remains flexible even after its frozen; but, it will become a bit hard in sub-zero freezers. If so, please letit thaw a bit before use.</span>