ST-4D - Zapco 4-Channel 640W RMS Class D Full Range Amplifier ST-4D - Zapco 4-Channel Class D Full Range Amplifier Power @ 2: 4 x 160 watts | Power @ 4: 2 x 320 watts | RMS Rated Power @ &lt; 0.05%THD Power @ 2: 4 x 160watts | Power @ 4: 4 x 100watts | Bridged @ 4: 2 x 320watts Class-D bridgeable 12V amplifier Dimensions in Inches : 6.7(W) x 2.2(H) x 7.87(L)