Malloom Portable USB Electronics Gadgets Novelty Item Powered Cup Mug Warmer ... Plastic and porcelain cup is not accepted in use of warmer. Steel cup is recommended, Size: 10*9.3*2cm Easy installation, no driver and other power source needed, just Plug & Play on/off switch with a Red Led indicator when warmer is turned on No risk of burn, with enclosure made of quality insulation material Keep coffee / tea / drink warm at 50-60oC Keep coffee / tea warm for any time interval