GP118-sw is 18” Subwoofer, it features premium-grade, long excursion, high power 18-inch transducer with 4-inch voicecoil, dual layer spider and triple-roll surrounds, interlocking feet and recess features allow for rigid vertical stacking, built-in handles for ease of transport, threaded pole cup for deploying a full-range loudspeaker on top, M10 fittings allows for suspension in permanent and portable applications, dual NL4 Speakon connectors, 18mm baltic birch plywood construction, 16-gauge powder coated steel grilles, available in black and white.