The design of the Union 5s rechargeable hand warmer is low-key and fashionable and enriched with simplicity. It offers four temperature levels, and the 360-degree heating surface can heat up in seconds. Users only need to click the indicator button to adjust the level to achieve a customized temperature and an ideal use duration. The first level lasts 15 hours, the second 11 hours, the third 8 hours, and the fourth 6 hours. Users can activate and operate the hand warmer by simply clicking, double-clicking, and pressing.