This is the Acoustimass 10 section. There has been IV series of these, the latest being 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, good for around 100 watts per channel 8 ohms classic redline speakers. These have limited bass response and were quite quickly updated. Still sound good if you can find a good one and don’t want extreme bass. Colour options black or white.