Power up with the Critical Universal Battery. One size might not fit all, but this universal battery comes pretty damn close. Compatible with the majority of rotary brands, the lightweight Critical Universal Battery is available in RCA and 3.55 mm connections. By transforming rotary machines into wireless devices, it allows tattoo artists to create freely without the interference of annoying cords. Depending on voltage and device, it offers up ten plus hours of work time. Voltage ranges from 4.5v to 13v.