Brimstone is the ultimate heated hunting muff. You supply the power, we supply the heat. This Mossy Oak Bottomland camouflage muff will be your constant companion throughout the cold season hunts. The muff comes with a removeable heat pad that attaches to the interior wall. The heat pad has an attached USB connector threaded from the interior wall through to the exterior pocket, where is it connected to the power supply/battery pack. Simply plug in your USB power supply (not included) for instant heat. The power pack fits into the front pocket for easy access. Disconnect the USB to turn the heat off and remove the battery pack when not in use and before storage. The heated muff has a whisper quiet durable exterior in camo Tricot on one side and blaze fleece on the other side. Both materials are bonded to a windproof/water resistant film to keep your hands protected from cold windy blasts. The muff is fully lined with a thick anti pill fleece that feels soft and warm against your skin. It has fleece cuffs to lock in the heat and keep the cold air out. An adjustable belt keeps the muff secured around your waist. Stay out as long as you want. The Brimstone heated hunting muff will keep your hands warm on the coldest of day and enable you stay out longer while you wait for the perfect shot to come around. The muff does not come with a battery pack. (You supply it.) The battery pack needs to be at least a 10,000 mAH pack with DC5V output. Using the correctly specified power pack, you will get at least 4 hours of 120°F degree heat.