More Heat, Less Waste. Ignik 24-Hour Compostable, Reusable High-Performance XL Body and Sleeping Bag Warmers are made from biodegradable materials, and come in recyclable packaging for more heat, with less waste. Each air-activated warmer provides up to 24 hours of heat, while the reusable AirBarrier Pouch, which minimizes air permeability, can save unused warmer heat for up to 72 hours, for intermittent use. 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 cold-weather camping, ski touring, hunting, and winter recreation, Ignik's ultra-efficient warmers are easily activated by removing them from the packaging and exposing them to air. Each warmer measures 4 x 5.3 inches, and weighs 136 grams; available in a pack of 4 pairs or a pack of 20 pairs.