The PHP-2 Polar Heat Pack is a set of 24 Polar Heat Packs which are Air activated warmers. These can be placed inside Polar Bear, Polar Mittens and Kodiak cases to keep equipment and accessories warm. The heaters are disposable and heat up to 130 degrees for more than 6 hours. The heaters are safe and odorless; they contain iron powder, water salt, activated charcoal, and wood fiber. They also work great for keeping your hands and feet warm