This is actually a 18650 Lithium Ion Cell Battery.
These round high capacity cells have been mainly used
in flashlight type applications but with its capability to be used as a
drop-in Rechargeable cell at 3.7V. This is a great battery option for those of you who need
a simple to install and replace cell with a lot of juice Over discharge may cause damage Full
voltage is not higher than the recommended 4.2V, and the discharge voltage is not less than 2.75V.