I got a pair of the new "powerstack" batteries last week in ratchet anticipation. they are rated at 1.7ah, are the thickness of the 2ah but narrower and lighter. they are lasting much longer than the 2ah in practice, and they are supposed to be "better" overall. amazon warehouse at $129 for the pair, dates on them are May of this year. still haven't gotten the tool lol.
I lost a 2ah somewhere, so I've got 1ea 2ah & 4ah, and a pair each 6ah and powerstack.