The Joyetech eGo-C Twist 650mah battery is an eGo-style battery with a modified circuit to enable the adjustment of output voltage from 3.2V to 4.8V. To increase the voltage, simply spin the knob at the base of the battery in a clockwise direction. To decrease the voltage, simply spin the knob at the base of the battery in a counter-clockwise direction. The Joyetech eGo-C Twist also has a lock/unlock feature that is activated by pressing the power button 5 times within 2 seconds. The 650mah battery should last about 6-7 hours of heavy vaping, but generally lasts most people a majority of the day. The Joyetech eGo-C Twist is incredibly reliable, consistent, and sure to satisfy your vaping needs.