Boston Acoustics Style Replacement Speaker, Woofer, Fits Boston Acoustics A-100, A-150, W-1010 Made in the USA! New materials last much longer than the original design! Size: 10-1/8 Impedance:4 ohms, Re:4.0 ohms Fs: 21 Hz, Vas: 10.96 cu. ft., Qms: 6.8, Qes: .148, Qts: .15, Xmax: 5.4mm