Compatible only with the following products by Sennheiser:
CX 1.00, CX 2.00, CX 150, CX 200, CX 215, CX270, CX 275s, CX 280, CX 281, CX 300, CX 300-II, CX 380, CX 400, CX 400-11, CX 475, CX 500, CX 6, CX 680i, CX 680i Sports, CX 685, CX 890i, CX 95, CX 980, CX 985, IE 4, IE 6, IE 60 WEST, IE 7, IE 8, IE 80, IE 8i, MM 30 G Black, MM 30i, MM 50 iPhone, MM 70i, MM 70s, MM 80i, OCX685i, OCX686