Many items from China are fake. Scandisk memory cards from China are mostly fake, for example.
You will be subject to duty if the value is �18 or above. This can put up to 40% on top of what you have paid, although you would be unlucky if it were that high.
If there is a problem with the goods, the cost to return them can be prohibitive, and painfully slow.
Unless you know the market, and your source is recommended to you, I would be very wary.
Take the time to read all the info you can - this is a good starting point:
http://tinyurl.com/j8kzh