This is the Acoustimass 6 section. There have been 3 series of these, the latest being an active bass module, giving superior bass response. Improved circuitry gives better range and higher overall sound output. This is the series I Bose passive 5.1 system. Designed for medium sized rooms and good for around 50 watts per channel 8 ohms classic redline speakers. These have limited bass response and were quite quickly updated, they still sound good if you can find a good one and do not want extreme bass. Colour options black or white.