From Teryn: "Yay...finally a power box that runs two machines! Two outputs...two machines at the same time. Switch between the two machines with a click of a button...super easy. This is the perfect power box for techs that use two different needle grouping for brows, eyeliners, areolas and lips. That's me and I know alot of you guys do to. Even if you use cartridge needles that are easy to remove and change out...you're putting your fingers by a contaminated needle increasing your risk of a needle prick...that freaks me out. This power box is going to rock your world! If you don't tend to use two different needles in your work one of our other Critical will serve you perfectly. Now read on for the manufacturers description".