The AVA EP9 has two modes - a Lining and a Shading mode. In the lining mode, the pen's power frequency runs higher than in the shader mode.
Voltage adjustment is done by tilting the pen respectively which allows you to stay focused on your artwork and ultimately streamlines your workflow.
Black EP9 is av3.5mm stroke machine which a perfect all-purpose liner and shader. Whereas, the Gray EP9 is a 4.2mm stroke machine which is used for pulling dark single-pass lines and color packing solid colors. Together, they are a forced to be reckoned with.
Check out the EP9 Artwork Showcase page to see the amazing artwork done with the EP9 pen tattoo machine.