Air-activated portable packets, no wires or batteries required. All natural ingredients. 3 year shelf life. Made in the Usa. The highly portable and air-activated Heatmax Body Warmers with adhesive are a use-anywhere solution to the frigid cold. Keep a couple in your car, first aid kit, or backpack for emergencies, or use them as a regular staple during any cold-weather activities, including skiing, hiking, hunting, fishing, or working outdoors. Designed to last for up to 12 hours, the Heatmax Body Warmers provide safe, comfortable warmth in the coldest of temperatures. Heatmax warmers are odorless, disposable, non-toxic, and nonflammable, so you can use them without worry. Made of natural materials, including iron powder, water, salt, activated charcoal, and wood fiber. The packets are simple to use. When you open the wrapper exposing the contents to air, the materials react together to produce heat through an extremely fast oxidation (or rusting) process. Users should allow 10 to 20 minutes for the warmers to reach their optimal temperatures, and can count on warmth for up to 12 hours.