XBees are so cute and tiny but if you're using them in a circuit you'll be annoyed to find that your classic 0.1" headers don't fit them! That's because they use 2mm spacing instead of 2.54mm spacing. That's why you need a special socket like this one.
This socket has 10 pins, 2mm apart. Check the datasheet (in the Downloads tab) for a detailed diagram. You can find a footprint for the XBee that works with this connector in our Eagle Library (its called XBEE)