Simply connect your charger to this vest's Type A cable, and it will warm up nicely. No special battery is required. The temperature is adjustable in three stages by pressing the button on the chest (the button color changes). Red (high) is the hottest. It warms the back, as well as the front (stomach) from the upper chest to around the navel. It's rare to have the heating element extend to the collar (under the chin). The back also feels good, and I felt like it gently relieved fatigue. The charger can be stored in the inner pocket. It's good for outdoor work as well, as your arms can move easily, not just indoors. The waist area has elastic. There are pockets on both sides. A simple instruction manual is also included (8th image). It's a 3XL, but it actually feels like an XL to a smaller 2XL. Operation confirmed (R7.11.14). I'm selling it at a low price because I prefer cash on delivery. Please specify either the post office or Yamato. Thank you for looking.