Translation of "想要买什么东西吗？" According to tatoeba translation of "Is there anything you want to buy?" is "想要买什么东西吗？" Is there use of 什么 and 吗 in one sentence? If there is not how can I translate"Is there anything you want to buy?" better?

http://tatoeba.org/eng/sentences/search?query=%E6%83%B3%E8%A6%81%E4%B9%B0%E4%BB%80%E4%B9%88%E4%B8%9C%E8%A5%BF%E5%90%97%EF%BC%9F&amp;from=und&amp;to=und
The 吗 is a modal to make the question more polite. Its also grammatically correct to say just 你要买什么? which directly translates as What do you want to buy? But it is a bit brusque.