This electric lunch box is made of food grade 304 stainless steel and uses a USB data cable to provide energy. It can heat food anytime and anywhere, and provides long-term insulation. The correct way to use it is to put hot food into the insulation bucket and connect the USB cable. It can maintain an inlet temperature of 60 degrees at any time. Please note that this is a long-lasting insulation tank powered by USB, not a quick heating tank.