The cup warmer mainly keeps your coffee, water, milk, tea, and other beverages at the perfect temperature for a long time. Use a thin-walled, flat-bottomed mug for the best warmth retaining performance. It's a beautiful and compact design, making it a great gift choice to show your care to your families, lover or friends on special occasions. Please note that we don't recommend using concave and thick bottom cups, as the heating will be slow and bad. This is not an electric kettle, it's designed to slow down the cooling speed of hot water and keep it warm throughout the day.