Do not buy the USB Mug Tea Cup Warmer as it is useless and worthless.
I saw the reviews for USB Mug Warmers and realised that it was possible that it would not get very hot, but did not expect such a poor performance as it delivers.
To put it into perspective the heat it generates is probably just enough to lift the temperature from cold by 1º or 2º and no more. For all intents and purposes the drink is still cold.
This item is RUBBISH and a WASTE of my MONEY