The N-Ferno 6990 Hand Warmer Packs are long-lasting and air-activated, instantly delivering up to 12 hours of heat. They're great for placing in your jacket pockets, gloves or other warming accessories. They're also easy to insert into built-in pockets in thermal accessories such as the N-Ferno 6980 Hand Warmer Muff, N-Ferno Hard Hat Liners or ProFlex Winter Work Gloves. Individually sealed pairs of warmers. To activate, simply open the pack. The all-natural ingredients will begin to heat up as soon as they're exposed to oxygen—no batteries required. You can also shake the pack to speed up the warming process. The N-Ferno Hand Warmer packs are non-toxic and made with all-natural ingredients. Plus, they're disposable and compact for easy use on the go. Packs are not reusable and should be disposed of after each use.