Pioneer UD-SW300D Single down-firing sealed enclosure for 12" shallow sub at Crutchfield
Kicker Comp RT 12 Inch Thin Down Firing Enclosure Package with 46CXA4001 Amplifier and wire kit - Creative Audio
KICKER COMPRT10" Down-Firing Enclosure - AudioWorks of Delaware | Turn It On! | Car Alarms - Remote Starters - Audio Systems - Navigation Systems - Multimedia Systems - Custom Car Rims & Tires - On-site Company Fleet Services
UD-SW100D - Downfiring Enclosure for 10" Shallow Subwoofer | Pioneer Electronics USA
Kenwood PA-W801B 8" Powered Down-firing Subwoofer in Vented Enclosure
Three exciting car subwoofer options
Kicker Comp RT 10" Down Firing Subwoofer Kit with Box: TRTP102-SK
PowerBass PS-ADF110T Compact downfiring 175-watt powered enclosure with 10" subwoofer - Breakers Stereo and Performance