Bose Style Replacement Speaker, Woofer, Fits Bose 501, InterAudio, W-1050 Made in the USA! New materials last much longer than the original design! Size: 10-1/8 Impedance: 6 ohms, Re: 5.7 ohms Fs: 27 Hz, Vas: 7.89 cu. ft., Qms: 4.1, Qes: .54, Qts: .48, Xmax: 6.1mm