Asdomo DC 12V Pre-wired Black Plastic Audio Power Jacks Noise Filter Ground Loop Isolator Suppressor for Car The Car Power Filter will bring you a good audio effect. There are 3 wires. Blue wire for input (12V), Red wire for output and black wire is groundwire. Wiring Color:Black, Red, Blue Feature: Power supply noise of igniter produces filtration effect, make the sound effect is better Total Length32cm / 12.6