I am curious as to what determins the size of band you get? I have noticed that some are 4, some are 10 and some are larger.

My doc determines size after going in. Every one is different, and I was surprised to get a 10cm/4cc band. I'm 5ft 6inch 367pounds at the time of surgery and thought I would need the biggest. lol

I believe the number you are referring to is now much fluid a band holds. It has nothing to do with the actual size (length) of the band. It really doesn't make any difference, it is just different manufacturer's make different capacity bands. So, for example, if you have a 4cc band and have 2 cc's in it, it would be similar to having a 10 cc band and having 5ccs in it. There are also different sizes of bands (the length when layed out before closed - I have an AP band and it is the smaller one. That is just because of the thickness of my stomach. If it had been thicker they would have put the large one on and I think there are also extra large ones. That's my understanding of how it works. I may not have it exactly right, but I believe that is basically it.