•Machine washable, set to gentle wash, can also be hand washed, remove the battery before washing •Super stretchy, double thickened and warm, soft and skin-friendly •the use of innovative spiral heating, heating wire inlaid in the sock layer, so that the heart of the foot and the back of the foot soles of the feet can be heated •Increased battery capacity, longer endurance •Two-hole USB cable, one cable for multiple uses Specifications: •Surface material: 51% viscose, 23% nylon, 26% polyester •Lining material: 100% nylon •Size: Free size •Battery capacity: 4000mAh •Charging voltage: 5V •Working current: 800mAh-1100mAh •Output voltage: 3.7V •Battery size/weight: 15.8 x 44 x 78.5mm, 0.08kg •Battery performance: -10°C~70°C battery can work normally, battery life is 500 cycles remaining 80% of the capacity •Charging time: all full time is about 4.5-5 hours (excluding ordinary cell phone chargers) •Gear: 3 gears •High: 4.5-5.5 hours, temperature 60-65°C •Mid: 6-7.5 hours, temperature 45-59°C •Low: 9-10 hours, temperature 39-44°C Package included: •1Pair x Socks •2 x Battery •1 x USB Cable •1 x English Manual