REL T/7x Subwoofer, 8 inch Front-Firing Driver, Arrow™ Wireless Port
Amazon.com: REL Acoustics Airship™ Wireless Subwoofer Transmitter Created for 212/SX, S/510 and S/812. Compatible with G1 Mark II. Not Compatible Serie T/i, Serie HT, Legacy Serie S or No.25. : Electronics