1.Used to adjust an amplifier's power level， stereo， equalizer or crossover volume form the dashboard or other remote locations.2.Adds sub-woofer level controls or balances a multiple amplifier installation.2.Compact housing allows the unit to be mounted virtually anywhere so control is at the user’s fingertips.4.Fine tunes the volume of any RCA line level signal you forto control.Adds a Dash Mounted Sub-Woofer Volume Control4 gold plated RCA's (2 RCA input & 2 RCA output)Level control knobGain 0db to -12db5cm x 4cm x 3cm (1.97in x 1.57in x 1.18in)