1941 - Large Warmer; 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. Unit UPC: 0-37137-01941-4