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. Each box includes 40 individually sealed pairs of warmers. Once activated, place the long lasting hand warmer inside a pocket or gloves. 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 825WP Winter Work Gloves. HOW TO ACTIVATE 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. Ideal for workers exposed to the elements while on the job in industries such as construction and mining. Plus, they provide much-needed warmth while hunting, fishing, skiing or enjoying other cold outdoor activities.