It may be important to find out if he is ordering you a better bottle that is ported or not. If he is ordering a ported one for you, then there will be a hole near the bottom that need plugging.
I have one plastic carboy. Not Better Bottle brand, but nonetheless, it uses a #10 stopper, while all of my glass ones use a #6.5. It is my understanding that Better Bottles have a larger opening at the top as well.