The Billow v3 is a complete redesign of the Billow v2. We took in all the suggestions from the community to make the Billow v3 the best it can be! When designing the Billow v3, we primarily focused on airflow, flavor, and the convenience of filling and building.
http://www.vapingbest.com/billow-v3-rta-tank-by-ehpro-eciggity-p-526