The XONE is the first BFX atty. The bfx system allows a better conductivity because of the bigger threads that screw directly to the cup. It is also leakproof because the center pin is sealed in the cup. The Xone atty is 18mm wide to get more flavour from your juice. It is good for both single and dual coil. Airflow is adjustable so it can be used for both MTL and DL vape.