What is the difference between the Zion and Milaana

The Zion has twice the battery life due to its to battery capacity. The Zion is voltage regulated meaning that the knob varies the voltage and keeps the voltage constant. The single battery is completely manual and runs direct off the battery voltage unregulated meaning it follows the voltage of the battery which drops as the battery is depleted. The single battery therefore is starts off at around 450 F and drifts down to 390 as the battery is depleted. To control the single battery the button must be modulated on and off. It requires a bit of technique but is easily mastered if you sense the strength of the vapor. Both produce the trademark Zion quality vapor. Each require a different amount of control.