More Heat, Less Waste. Ignik 8-Hour Compostable, Reusable High-Performance Foot Warmers are made from biodegradable materials, and come in recyclable packaging for more heat, with less waste. Each air-activated warmer provides up to 8 hours of heat, while the reusable AirBarrier Pouch, which minimizes air permeability, can save unused warmer heat for up to 72 hours, for use as needed over several days. Ignik heat is provided by 98 percent biodegradable natural minerals, combined with oxygen, and the contents of the warmers can be composted after use. Ideal for slipping into a boot or shoe while camping, hiking, hunting, snowshoeing, skiing, dog walking, or participating in other cold weather activities. Ignik 8-Hour Compostable Foot Warmers are easily activated by removing them from the packaging and exposing them to air for 2-5 minutes before inserting in a boot or shoe. Available in packs of 4 pairs or 20 pairs; each warmer measures 3.4 x 9.8 inches.