Bazooka BT6024DVC BT Series 6-1/2" Bass Tube® with dual 4-ohm voice coils at Crutchfield
2PC Subwoofer Speaker Accessories Bass Tube Plastic Car Reflex Port For Woofer Karaoke Home Theater Hifi Professional Audio|Speaker Accessories| - AliExpress
12" inch EMPTY Torpedo TURBO BASS TUBE Sub Woofer HQ Car Audio Speaker Box VWLTW | eBay
EMPTY 10" Torpedo TURBO BASS TUBE Sub Woofer HQ Car Audio Speaker Box VWLTW | eBay