These hand warmers are designed to solve the biggest problems you face with air-activated warmers; providing reliable, consistent, and more heat with less waste. The contents are safe, all-natural, and biodegradable. Plus, the AirBarrier™ pouch keeps more air out for more reliable heat - up to 10 hours each so you can stay warm for longer on all your winter adventures. The resealable top gives you control to use the warmers when you need them. Store unused open warmers for up to 72 hours later.