This heat vest is fitted with the new I-Warm 4.0. By using the app in your smartphone, the temperature is set individually on each of the three heat panels. There is also a built-in thermostat function. Design and construction is totally new. Filling is made with RDS-approved down. Power Bank, 10 000 mAh is included. The heat vest is meant to be a second layer garment. Please choose a tight size for best heat function.