Included: BLX4 single channel wireless receiver; BLX1 bodypack transmitter; SM31FH Headset Condenser Microphone; PS23 power supply and URT2 rack tray (optional accessories). SM31FH Wireless headset microphone featuring moisture-repelling hydrophobic construction for use in fitness instruction. BLX1 Bodypack Transmitter The BLX1 bodypack has a lightweight and durable design. Ergonomically designed to fit comfortably in hand, with adjustable gain control. For use with BLX Wireless systems. BLX4 Single Channel Receiver The BLX4 single channel wireless receiver is a durable receiver with simple set-up, intuitive controls and microprocessor-controlled internal antenna diversity. Available in four frequency ranges: BLX H8 (518-542 MHz)BLX J10 (584-608 MHz)BLX K12 (614-638 MHz)BLX M15 (662-686 MHz)