I have a bunch of them. They get around 6-8" max from what I've read. They are a VERY tough crayfish/lobster. They don't use their big claws for much, but when they do its for fighting and muscling around others. As long as they have nice caves or places to hide they usually are pretty peaceful towards others. From what I've seen, they don't really seem to hunt fish and they like to really roam in the dark. I drop frozen peas in there at night (when the lights are off and they seem to love them.
Toad
Toad