Foot Warming Packs: Self-contained packs activate when exposed to air. Provides warming to full foot and will fit in shoes or boots. 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, Foot style warms up to 7 hours Application:, Construction, Freight/Baggage, Drilling/Mining, Oil/Gas Refining, Iron/Steel Work, Delivery/Service, Landscaping/Grounds, Cold Storage/Warehousing, Material Handling