Bose Acoustimass Flush Subwoofer for FreeSpace 3 Systems (Black)High performance, extended range systems designed for small to medium sized installed applications requiring high fidelity and extended bandwidth reproduction of voice and music. Surface and flush components can be mixed and matched to provide greater flexibility to suit a wide range of applications. For indoor applications only. Features: Low frequency loudspeaker featuring one 5. 25 (133mm) woofer that delivers deep, non localized bass down to 40 Hz