"With incredible energy retention, these Uniross batteries come pre charged and are ready to use out of the pack. Each battery holds 70% of its charge over 12 months and replaces up to 1000 ordinary Batteries."
These are 1600mAh, so smaller capacity than the 2100mAh ones in the recent deal at Play - but they're also a good deal cheaper. Useful if you want to carry a spare set without having to worry about topping them up too often.
Don't forget 4% Quidco.