Technical Specifications of CLK!1280: Variable Voltage: The rotational wheel adjusts voltage in the following increments: 3.5, 3.8, 4.0, 4.3, 4.5, 4.8, 5.0 Standby current: 50u A max Maximum output current: 3.5 A Maximum output wattage: 15 W Clearomizer Resistance: 1.2 ohm (minimum), recommendation 2.5 Ohm Battery: Built-in 1280 m Ah polymer Li-Ion rechargeable battery. Charging: Micro USB (Universal Serial Bus) DC5V/500m A Short Circuit Protection: 0.6 +/-0.2 ohm Notice: The red LED will blink six times & turn off if the rotational wheel is not in place. To set your desired voltage turn the rotational wheel to the left or right until you hear an audible click. When adjusting the voltage with the rotational wheel always check to ensure the wheel is set to your desired voltage.