Hand Warming Packs: Self-contained packs add heat anywhere when exposed to air. Features, To activate, just open the pack, All natural ingredients heat up when they contact oxygen, Seal from oxygen in Zip-Loc bag and reuse the next day, Hand style warms up to 12 hours Application:, Construction, Freight/Baggage, Drilling/Mining, Oil/Gas Refining, Iron/Steel Work, Delivery/Service, Landscaping/Grounds, Cold Storage/Warehousing, Material Handling