Cup USB Electric Warmer. its real work?

[A1ex]

I intersting buy this product
http://goo.gl/xt06yf.

I want to know if its real keep warm the tea?

thanks

[qianli]

Theoretically speaking it would not work. It is rated at 2.5 W, which means it can only increase the temperature of 250 mL water by 1 degree C in 7 minutes. And that is in ideal conditions with no heat loss.