Amazon.com: DS18 SB10A 10" Shallow Subwoofer Enclosure with Built in Amplifier – Car Audio All in One Amplifier and Subwoofer Bass Package 700 Watts Power – Great Stealth Car Subwoofer in Box
Car Compact Subwoofer 12 inch Passive Radiator Slim Enclosure 900 Watts VIBE 5060661892821 | eBay
Kicker 49PTRTP12 Compact down-firing 500-watt powered enclosure with CompRT® 12" shallow-mount subwoofer and passive radiator at Crutchfield
Subwoofer Specific, Rockford Fosgate, R2 Subwoofer – Atrend USA