The re-usable hot button hot Pack instantly becomes hot once the button inside the Pack is activated. The Pack remains hot for at least 30 minutes. Re-usable Pack is recharged and made ready for a future activation by boiling it for approximately 10 minutes. The activation and recharging of a pad can be repeated at least 100 times. The hot button contents are not harmful; they are common non-toxic food additives. Activate pad by gently flexing disk within the pad back and forth until pad starts to crystalize; pad will heat to approximately 130°f (54°c). for cold Pack refrigerate do not freeze. To return to liquid state wrap pad in cloth, place in boiling water for 5 to 12 minutes. Oversize - 10" x 11".