My male is right at a foot. I've probably had him for a little under a year now, and he's still growing. He had a spell (while breeding) where he almost stopped growing for a couple months, then once separated he exploded again. He's put on another inch over the past month to month and a half. Boggie's is the biggest I've seen (granted only in a pic). I remember when he got it at like 13". The length of time since, and the 2" of additional growth, gives hope to continuous growth. The biggest I've seen in person other than my own, was a female probably just a bit larger than my male. All that said, I have searched the net, books, everywhere, looking for these 18" beasts, and have yet to find anything remotely close.