MTX Audio subwoofer in a vented tube style box with a built in amplifier built into the back of the speaker box. Everything works perfect and it sounds even better. Only reason I'm even coming off of it right now is because I have a different set of speakers that I'm currently using, so I have no use for this one anymore. Perfect for a car, the right amount of bass, not too much, but just enough to let you know that there is a subwoofer installed. $75 obo... Also open to trades, just let me know what you got and I'll tell you if I'm interested or not.