High capacity of battery: capacity of 1500 mah enables artists to work for a long duration of 4-6 hours. When the battery has run down, the rca connector can be replaced.Simple operating system: led screen shows battery, timing, and voltage more clearly. Artists can easily adjust the voltage by pressing buttons.Instant start-up function: start-up function will be automatically activated at power on. Even large rows of needles can be used easily.Variable stroke: 2.4 2.7 3.0 3.3 3.6 3.9 4.2 Mm cfor all artists from tattoo to smp.