This Samson AirLine 99 Rackmount Wireless Microphone System brings fitness and aerobics instructors a wireless headset microphone system with quality sound, water and sweat resistance, dependable performance, and simple setup. The AH9 micro transmitter is mounted directly on the Qe headset to offer a true wireless experience with no beltpack and no cable, allowing complete freedom of movement during workout, dance, yoga, or spin classes.