This is a powerful single 18” passive subwoofer in a vented enclosure. The upgraded 18” woofer has a 4” voice coil and a weatherproof cone. The cabinet is well braced and has four ports for excellent high-level output. It comes with a top hat for a pole-mounted satellite speaker. Optional second top hat shown here so it can be laid on it’s side for a more stable base. The TL 18.1 is also available in permanent a installation version with no handles, top hat, and has a barrier strip connector. Optional wheel board provides stable portability.