Relief Pak Hot Button Reusable Instant Hot Compress - small - 3.5" x 5.5"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