Fast heating: Built-in high-quality carbon nanofiber heating element, using fast heating technology, easy to use. Rechargeable lithium-ion battery, heating up to 4-8 hours, easy to remove the battery. The kit includes: a pair of heated socks, two 3.7V rechargeable batteries, a charger and instructions.Safe to use: Built-in thermal protection module and 3-level temperature control, intelligent temperature adjustment. Using carbon fiber heating, far infrared rays are beneficial to the human body and stimulate your blood circulation. The material is soft and suitable for both men and women: The material is soft and breathable, and has excellent moisture absorption and perspiration ability. It will keep your feet dry, comfortable and warm on cold days. Use soft and elastic knitted material, stretchable, size unisex. Unique washing performance design: Nano carbon fiber has excellent flexibility and plasticity. It can be washed by hand or machine.Wide range of applications:Suitable for various indoor and outdoor activities in winter, such as hunting, hiking, cycling, skiing, mountain climbing, outdoor work, etc.