Say goodbye to one-use disposable heaters. The UST Reusable Hand Warmer is a temporary warming tool for whenever you need an extra heat source. Whether you're at home or out in the elements, this Reusable Hand Warmer delivers time and again! The UST Reusable Hand Warmer provides up to two hours of heat. It heats up to 130° F (54° C) in just 15 seconds. Sodium acetate and water are activated by bending a metal disk inside the pouch. When heat runs out, the warmer can be rejuvenated with boiling water. Environmentally friendly.