Purchased 2-3 years ago and used about 10 times. Please check the photos and consider purchasing. ◇ Cool your body in 3 easy steps! ① Fill the tank on your back with about 150ml of cold water. ② Charge the tank on your back with a frozen PET bottle! (Compatible with PET bottles up to 650ml) Alternatively, you can use ice. Small ice packs that fit in the tank can also be used. ③ Turn on the battery. The battery is also easy to operate. ◇ In the summer, fan-equipped clothing can sometimes make you feel hotter because the fans draw in hot air in high-temperature, high-humidity environments. ◇ With water-cooling clothing, cold water flows directly near the body, so you can get a higher cooling effect, especially in hot environments, compared to cooling with air. ◇ Also, you can hydrate with the melted PET bottle drink, and frozen PET bottle drinks are sold at convenience stores and drugstores nationwide in the summer, making it easy to charge with frozen PET bottles. ◇ The dedicated battery has a timer function and can be adjusted in 3 stages to suit your usage scenario. (① Continuous use, ② 20 seconds on - 45 seconds off, ③ 20 seconds on - 1 minute 30 seconds off)