The iKrusher Slim Pen battery is designed to utilize 510 cartridges. The iKrusher Slim Pen battery features a single button operation, 350mAh capacity, variable voltage, and Pass-Through charging. The voltage can be switched with three quick clicks on the button and the LED light will change the color according to the voltage red - 2.8V, green - 3.3V, and blue - 3.8V.