Brand new and high quality Features: Just gently turn the knob of the controller. Different frequencies can make the song sound different. It feels very good and is very convenient. Connect the RCA from the output of this controller to the amplifier and connect the car stereo output to the RCA input of this unit. Perfect for a sub amplifier volume control. Used to adjust an amplifier's power, stereo, equalizer or crossover volume from the dashboard or other remote locations. Adds subwoofer level controls or balances a multi-amplifier setup. Compact housing allows the unit to be mounted virtually anywhere so that the control is at the user's fingertips. Fine-tunes the volume of any RCA line level signal you can control. Simple input and output connections, no extra cables needed. Connect the RCA from the output of this controller to the amplifier and connect the car stereo output to the RCA input of this unit. Specification: 4 RCA: 2 RCA input and 2 RCA output Level control knob Frequency range: 150Hz - 40Hz Volume gain range: 0db to -12db Material: metal Dimensions: 48x56x41mm/1.89x2.2x1.61inch Color: Black Quantity: 1 pc Note: 1.Please allow 0-1cm error due to manual measurement. Make sure you do not mind before bidding. 2. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thanks! Package includes: 1 x Car Stereo Controller