That might fit but that's a nunchuck battery for a PEQ box. What you really want for a Kraken is a large battery similar in size to the POS nicad one it comes with
A smaller battery will rattle inside your stock. You'll want an 8.4v or 8.6v large battery (I can't remember if the Kraken has a large or small tamiya connector) since the Kraken has like an m110 or m120 spring in it.