The BIG Larry PRO rechargeable battery is a high performance rechargeable li-ion battery with an integrated battery overcharge & discharge protection circuit. It is for use only with the Big Larry Pro and 2nd Generation SLYDE KING flashlight.
Q: Can I use the 6640BAT rechargeable NEBO battery in other devices that use an 18650 battery?
A: No, although it is an 18650 type battery, the 6640BAT has contacts arranged specifically to interface with only the BIG Larry PRO and 2nd Generation SLYDE KING flashlights.
It fits, it charged, it made my flashlight like new again. Yay!
Exact Replacement others could not provide. Quick top off on the charge and back in bright light again.