Universal Amplifier Bass Rca Gain Level Volume Control Knob For Car Home Black Mount in or under the dash Dash Mount Amplifier Level Control for Volume Adjustment Can Adjust the Amplifier Gain While DrivingPerfect for Balancing the System to Change Music Styles Simple in and out connections, no additional wiring needed Interface: 2*RCA Output; 2*RCA Input The distance between the mounting holes: Approx. 4.5cm size:Line length is about 18cm Material:Plastic + metal colour:black Package Contents: 1 * Volume controller 2 * screw Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.