How big do BTAs get?

[Cheebs]

I'm sure it's been asked before, but how big can BTAs gt before they split? Do they keep growing? Mine is almost a foot accross at times, can they get even bigger? Pics would be awesome

 

[Toddrtrex]

Here is a picture of mine right before I sold it. It wasn't fully open in this shot. I would guess it was around 15", and it had split about a month before hand.

( on the right hand side, in my 75 gallon )