Heat Factory Toe Warmers are designed to heat in the restricted air environment of a shoe or boot for up to 6 hours. The half moon shaped Toe Warmer adheres to the bottom of your sock for comfortable warmth. Ideal for daily use in shoes, ski boots, or whenever toes are cold. Not intended for use in open air. Great for fishing, hunting or outdoor activities. The Heat Factory toe 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 toe warmer pouch is made of soft cloth lined with a very thin layer of porous plastic for maximum durability. Peel back the adhesive backing and press warmer to outside of sock underneath toes. The Heat Factory Toe Warmers last approximately 6 hours and measure: 3.5" x 2.75". Sold as pair.