Avaya B100 Expansion MICS: Compatible with Avaya B149 Conference Phone;  Compatible with Avaya B159 Conference Phone; Compatible with Avaya B179 Conference Phone;  Increases range of Avaya B100 series conference phones up to 750 feet; For use when more than 10 participants use B100 series conference phone;  Comes with 4 ft or 8 ft connector cables.