Amazon.com: Speaker Subwoofer Woofer 4 Ohm 25~35w 1pcs for JBL Xtreme 2 and Xtreme 1 : Electronics
For Xtreme Series 4.5 Inch Special Bass Passive Radiator Assistant Woofer Radiation Metal Diaphragm For 3-5 Inch Speakers Use - Speaker Accessories - AliExpress