The eGo-C Twist 650mAh battery is another advanced vision based on eGo-C original battery. With a modified circuit to enable the adjustment of output voltage from 3.2V ~ 4.8V. With a smart Buck-Boost converter inside, you can spin the knob at the bottom to adjust the output voltage depending on your need.Specs: Capacity: 650mAh Length: 3.85in Diameter: 0.045in Voltage: 3.2V ~ 4.8V Accurate adjustment of the output voltage, intensified short circuit protection, discharge and overcharge protection, atomizer protection, low voltage protection.Includes: 1 eGo-C Twist 650mAh Battery Compatible:510/510-T atomizers, cartomizers, Clearomizers - Joye eGo/T/C atomizers, cartomizers, Clearomizers There are altogether 8 grids on the knob at the bottom, and each represents 0.2V. Spin the knob in a clockwise direction to increase output voltage and spin the knob anticlockwise to decrease output voltage. Higher output voltage gives more vapour. You can adjust the output voltage very easily and enjoy the whole vapor time.