X Pole Ceiling Base Diameter?

Hi ladies, Only 15 days til I get my pole! (Woop woop!!!) and my OH is starting to ask questions....he wants to know how it goes up etc - so I showed him the instructions etc and he seemed happy enough. But now he's asking me what the diameter of the ceiling base is? I can't find this info on the site I'm buying my pole from so wondered if any of you lovely ladies knew or could find out for me? -x-