• Activate for instant heat: flexible disc to activate heat instantly. The temperature will rise up to 55 degrees Celsius. The approximate duration of the heat is 40-60 minutes. • Reusable hand warmers for the cold winter, outdoors, camping, skiing. Suitable for children and adults in outdoor activities. • Use them again and again: reactivate by gently boiling in water for 5 minutes or until the crystals are completely liquefied. • Safe and natural heat: ingredients: durable PVC bag, 12% distilled water, 88% sodium acetate, metal disc. • CAUTION: When boiling, wrap it in a cloth or stir constantly. Do not let it remain in contact with the bottom of the pan.