(1) Single Use 12-Hour UnderWarmer unisex, heated compression fitted, base layer shirt. Compresses against your skin to keep your upper body warm. NO BATTERIES REQUIRED like most heated jackets, heated vests, and heated gloves. HOW DOES IT WORK? It’s Air-Activated. So it never needs a charge! When ready to use, simply remove from its packaging and put it on. The 8 heat packs are built right into the disposable shirt. No need to “shake” or “break” them. Feel the heat in about 10 minutes. Up to100°F/38°C COMPRESSION FITTED: The UnderWarmer is made of a soft, lightweight compression material. The compression fit will keep the heat elements tight against your body, delivering over 12 hours of heat where you need it the most. Safe to wear directly against your skin. HOW MANY TIMES CAN I USE THE UNDERWARMER? Wear it once for 12 hours, or get multiple, shorter uses! Here’s a tip! By resealing The UnderWarmer in your own ziplock /air-tight bag, it can be used again. Understand that after12 total hours of producing heat, the packs will harden and The UnderWarmer is disposable. PERFECT FOR COLD WEATHER: You always thought that you had to choose between your favorite winter activity and staying warm. But no longer. Whether you're deer hunting, ice fishing, hiking or camping in the cold outdoors, the UnderWarmer heated shirt will make it a wonderfully warm experience and your must have hunting accessory. GREAT FOR FOOTBALL FANS: Gift your tailgating spouses and buddies (or yourself!) with a way to enjoy cold weather football games AND stay warm for the whole day. QTY (1) UnderWarmer Single Use (12 Hour) Unisex-Compression Fitted Heated Shirt with Air-Activated Heat Packs Enjoy your winter activities like never before!. The UnderWarmer heated shirt is convenient, super comfortable and best of all - it works really well. The UnderWarmer was specifically designed to be affordable and convenient for the everyday guy or gal spending a long day in the cold. That’s why UnderWarmer has some very specific features, like instant air activation (just take it out of the package) and compression fit (so you can feel every bit of heat pressed against your upper body,). For just a few bucks, you have a portable, wearable radiator, ready to go the moment you are. Unlike hand and foot warmers, which only help extremities that have already gotten cold, the UnderWarmer PREVENTS those extremities from ever getting cold. How? By keeping your core warm - because a cold body core is the cause of icy extremities. Best of all, unlike all those bulky coats and layers you’ve tried, the Underwarmer is extremely lightweight and won’t slow you down. You CAN stay warm for the entire day, even in negative digits. Just grab your UnderWarmer! Instant Air Activation Single Use No Batteries Compression Fit 8 Built In Heat Packs Reaches up to 100°F/38°C Unisex Lasts up to 10 hours. SEAL AND REUSE The UnderWarmer is essentially a single-use product. However, If only worn for a few hours place it in an air tight bag and it will stop producing heat. Essentially going dormant.