The Hotronic S4+ Power Plus Single battery pack is a high-quality accessory designed for winter sports enthusiasts. With this brand's reputation for reliability, the product provides warmth and comfort during cold outdoor activities such as skiing, snowboarding, or snowshoeing. The single battery ensures long-lasting heat, making it a practical and efficient choice for staying cozy in chilly weather conditions. This item is brand new, from a new custom S4 power plus set. The battery shown is the one for sale and I tested it in my ski boot indoors, on heat setting 3/4 it powered boot warmer for 7 hrs 5 minutes which is consistent with well functioning new battery (see chart in listing photos).