Cambridge - Aero 2 Bookshelves (Walnut) Drivers: 1 x 46mm (2") BMR, Woofer: 1 x 165mm (6.5"). Frequency response 40Hz - 22kHz. Recommended maximum amplifier power: 120 Watts. Impedance: 8 Ohms compatible. Dimensions (W x H x D): 203 x 370 x 311mm (8.0 x 14.6 x 12.2")