"Due to the popularity of our portable products in regions with cold climates, we have switched the ArGo / Air II battery to one that can perform much more reliably at temperatures below freezing. Rest assured the new batteries are even higher quality, with higher mAh, better overall capacity, longer life, and greatly improved performance in cold temperatures." from Arizer Support.
The new specification is the Samsung 35E, just wanted to pass this along as the spec given further up this page was for the old Panasonic NCR18650B cell.