The Metrix Variable Voltage 510 battery is a great product for oil/e-liquid. The Metrix Pen features a 650mAh capacity and variable voltage settings. Adjust your settings based on the type of e-liquid or oil you are consuming. The Metrix Pen is designed for the beginner who is looking into concentrate products and wants something affordable, discreet and simple-to-use. This battery is one of the most slim batteries on the market. Simply inhale to activate and a light will indicate that it is working. Perfect for pre-filled cartridges. Simply screw your cartridge onto the Vertex battery and you are ready to begin consuming!