SPECS: Dimensions: 4" x 5" Weight: 0.2lbs Materials: iron, vermiculite, salt, other natural materials 98% biodegradable; contents inside warmer sack can be composted after use DESIGN & DETAILS: Air-activated design Two warmers, one for your feet and one for your torso, deliver up to 24 hours of heat to keep you toasty in your sleeping bag on chilly nights For fast heat, remove the warmer, shake it, and enjoy industry-leading heat output in about 5 minutes For prolonged all-day heat, remove the warmer, shake it, and put it back in its pouch Heat from natural minerals and oxygen is safe and comfortable Compact and portable design Resealable and reusable temperature regulation envelope allows you to save one hand warmer for the next day