Zapco ST-104D.BT 460 watt 4 Channel Amplifier with Bluetooth Micro chassis: 3.75 x 1.38 x 8.39 inches. 4-Channel, full-range, Class D amplifier. 460W. RCA and speaker level inputs; Auto-on with speaker level inputs. Bluetooth music streaming. Variable input gain control; Variable electronic crossover; Variable bass boost control.