Heat Factory Large Warmers generate heat for up to 20+ hours. All Heat Factory warmers are non-toxic, safe, and odorless. Large Warmers can be used in pockets, stadium cushions, sleeping bags, and many other Heat Factory accessories. With Heat Factory warmers you will never be cold again. The Heat Factory warmer is a soft, light-weight pouch containing an inert mixture of iron powder, charcoal, salt, water and vermiculite. When exposed to air, a natural exothermic reaction generates consistent and prolonged heat. The pouch is made of soft cloth lined with a very thin layer of porous plastic for maximum durability. The warmers are odorless, non-toxic and air-activated. Great for fishing, hunting or outdoor activities. The Heat Factory Large Warmer measures: 6.5" x 5" and comes 1 per pack.