Unworn. I have confirmed that it cools down when connected to the battery. It gets quite cold, but -30°C is an exaggeration. Peltier vest that achieves a perceived temperature of -30°C. - Model Name: Peltier Vest - Cooling Technology: Equipped with cooling plates - Battery Capacity: 30000mAh - Usage Time: Approximately 9-11 hours on strong mode, 7-10 hours on weak mode - Perceived Temperature: -30°C [Perfect for Free Size & Heatstroke Prevention Goods & Gifts] A full set that can be used immediately upon arrival: Peltier vest body * 1, battery * 1, controller * 1, charging cable * 1, instruction manual * 1. Free size (equivalent to S~5L), unisex specification. Please purchase only if you understand that there is no warranty, etc.