The eGo AIO Pro's sub-ohm pen uses our best anti-leaking design with a larger 4ml e-juice capacity. It is powered by a built-in 2300 mAh battery. Refilling is easy with our newly redesigned top cap. Simply unscrew and fill. The newly improved airflow control system brings much better airflow. It is simple and convenient to use, and is available in several colors. The indicator light has a large choice of colors as well. Its simplicity and efficiency make eGo AIO Pro a great subohm pen for anyone.