Rechargeable 14500 (AA) Lithium - UltraFire

This is the lower but cheaper grade for you cheapasses, if you want your electronics to be safe, use the CGI ones. We will not guarantee anything, we will just laugh if anything spoils.

14500 Rechargeable Lithium Ion for use with your compatible flashlights

Capacity: 900mah
Voltage: 3.7 volts

Comes in a pair of 2 pcs

As usual, when using such high powered batteries, do ensure your flashlight is able to handle the voltage before even slotting them in.