2 BATTERIE RICARICABILI 18650 lithium 2500m

Pros: Great price
Simple to use
Actually works very well for rechargable
Protection circuit
Works great in my 2 lights - 15739 / 22570

Cons: The diameter is too big to fit into a genuine Surefire Ultra 2. I specifically read a review where a 18650 was used and was looking forward to using a rechargable in my U2.

Other Thoughts: I bought the 3944 charger in the same order. The work great together. No fitment or length issues.
I haven't run them down to 2.75V yet but the recharge time has varied from 1hr to 2hrs on the 3944 charger.