The Steroplast Reusable Hot/Cold Pack is ideal for providing temporary relief from muscle aches, back pain, sinusitis, and menstrual cramps. To use for heat therapy, place the gel pack in the microwave for approximately 30 seconds on high temperature. Check the temperature after this time and immerse the pack in water that has been brought to a boil and removed from the heat for 4-10 minutes. For cold therapy, store the pack in the freezer for approximately 1 hour. This pack is also suitable for reducing swelling, toothache, temporary relief of headache, and reducing fevers.