Only tried on and never used. Selling because the size doesn't fit. Comfortable cool vest equipped with Peltier cooling technology, can be used for a long time with a 10,000mAh battery. - Model: PV111 - Cooling method: Peltier - Battery capacity: 10,000mAh - Input terminal: USB Type-C - Size: M - Material: Mesh ■ Set includes vest (P119), 4 Peltier devices, a changeover switch (P1882), a dedicated battery, and a charging cord (P1883). ■ Designed not to interfere with the fans of comfortable wear. ■ Designed not to interfere with full harnesses. ■ Peltier devices are fixed with Velcro. ■ Cooling and heating can be switched with the switch. Size: M Length: 54 cm Shoulder width: 34 cm Chest size: 85~93 cm Hem circumference: 76~84 cm Cool Switch Cooling Temperature Difference Continuous Operating Time Strong (red light) -20℃ Approximately 4 hours Medium (blue light) -15℃ Approximately 5 hours Weak (green light) -10℃ Approximately 6 hours Hot Switch Heating Temperature Difference Continuous Operating Time Strong (red light) +50℃ Approximately 6 hours Medium (blue light) +45℃ Approximately 8 hours Weak (green light) +40℃ Approximately 10 hours Thank you for viewing.