This remote amplifier level control adds sub-woofer level controls or balances a multiple amplifier installation. Fine tunes the volume of any RCA line level signal you wish to control. Connect the RCA from the output of this controller to the amplifier, and wire the car stereo output to the RCA input of this unit. Dash mount amplifier level control for volume adjustment. Can adjust the amplifier gain while driving. Perfect for balancing the system to change music styles. Simple in and out connections, no additional wiring needed. Just rotate the button gently, and the different frequencies can make the song sounds different. Item Name: Car Bass Controller Material: ABS + Copper Core Quantity: 1Pc Voltage: 12V Compatible: Car Universal Features: Volume Adjust, Durable, Easy to Use, Car Accessories Note: Due to the light and screen setting difference, the items color may be slightly different from the pictures. Package Includes: 1 x Car Bass Controller Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Sold by-YJL official store