Useful Coffee Warmer heats and keeps beverages warm at over 60 degrees (celcius). * Power Source: Computer USB for warming plate and hub, button battery for clock. * Whole Unit: 135mm x 63mm (diameter x height); Heating Plate: 82mm diameter * Energy Usage: approx 2.5W; USB Cable: 95cm long; Weight: 236g * Package Contents: 1 x Mug Cup Warmer; 1 x Instruction Sheet(English Chinese)