in or under the dashboard In-dash amplifier level control for volume adjustment Can adjust amplifier gain while drivingPerfect for balancing the system to change music styles Simple input and output connections, no additional wiring required Interface: 2 * Output; 2 * Input The distance between the holes of: approx. 4.5cm Size: The line length is about 18cm Material: Plastic + metal Color: Black Package Contents: 4 * Volume Controller 8 * Screws Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in a little different from the real thing. The measurement allowed error is +/- 1-3 cm.