Note: This warm shoe has no battery inside, it is USB port. When you warm them up for a minute, the shoes will start to warm up. When you use them, you need to keep charging them so they stay hot. Specifications: This electric heating shoe can heat up for a long time.High-conversion carbon fiber is used as a heating material. It can also be heated directly by the charger. Specifications - Item name: washable USB heating shoes - Size: For women(35-39) / For men(39-43) - Color: pink/silver gray - Max temperature: 55 - Length of cable:150cm Condition:100% new and high quality Package Included 1 Pair of heating shoes Friendly Tips: Please allow minor error of measurement,due to manual measurement. Due to the different display and different light, the picture may not reflect the actual color of the item. Thanks for your understanding