Z-18 V.4 D2 - Sundown Audio 18" 1750 Watt RMS Dual 2-Ohm Z4 Series Subwoofer Z-18 V.4 D2 - Sundown Audio 18" 1750 Watt RMS Dual 2-Ohm Z4 Series Subwoofer Mounting Depth: 11.39"