This enclosure fits (two) Type S 12" Alpine Subwoofers & (two) PDX Alpine Amplifiers. This setup is completely hidden under the rear hatch-mat. It was build in the space where the spare tire well is located. This leaves the entire rear hatch with open space, creating the illusion that there is no audio system installed. This bimmer will rock any block it drives through! The custom enclosure is tuned perfectly to maximize the output of both 12" Type S Subwoofers. These PDX Amplifiers were engineered for the highest sound quality with less than .05% distortion threshold rating. The bass this bimmer makes surprises everyone near it! Everyone asks us "WHERE ARE THE SUBS?" See for yourself in our YouTube video now!