Compare to its predecessor Z-380, the primary improvements and differences can be seen on Z-390 are : -Z-390 comes with a 4-Liter fluid tank which helps reducing the times of refilling. Better for operations when the machine is rigged up in a higher location where refilling is more time-consuming. -Due to the larger fluid tank, the Z-390?s body is slightly bigger. -Z-390?s haze output is raised approximately 30% higher.