Belt size and suppliers

Well, I have decided that I will be using a belt for my x axis. I
will still be using screws for my y and z. Now for the next question.
Is there a difference in belt size? I think there is so maybe what I
am asking is what size belt and motor(stepper) should I be looking at
for my 10' x axis. I will be searching ebay for any used ones but I
think it will have to be a special Item at its size. Thanks in
advance for any help.

Thanks
Mike