The Fitness Headworn Wireless System BLX14E/SM31 specially conceived from SHURE includes a Single Channel Receiver (BLX4), a BLX1 Bodypack Transmitter and a SM31FH Cardiod condenser headset microphone that repels moisture. The moisture-repellent cartridge housing ensures a long product life by protecting the microphone from the corrosion damage. The Single Channel Receiver (BLX4) features professional wireless technology. Plug & Play and Quick Scan make the receiver currently ready for use.
SM31FH Headset Microphone Features:

Wireframe headset fits securely and comfortably for fitness and aerobics instructors
Moisture-repellent hydrophobic fabric protects the microphone cartridge from harmful corrosion that occurs in humid environments
Flexible gooseneck provides discrete adjustment capabilities to optimize placement for greatest isolation
Lightweight and low-profile design won't fatigue instructors during high-impact use TA4F (TQG) connector is compatible with any Shure wireless bodypack
Included windscreen tames plosive, breath, and wind noise for clean and intelligible sound
Tailored frequency response ideal for crisp, clear vocal reproduction
Legendary Shure precision engineering for durability and performance
BLX4 Single Channel Receiver Features:

XLR and ¼" output connectors
Two-color audio status indicator LED Green: Normal audio levels, Red: Excessive audio levels (overload / clipping)
Compatible Systems per Band: Up to 12 (region dependent)
Weight: 998 g
BLX1 Bodypack Transmitter Features:

Battery Life: Up to 14 hours
Typical Operating Distance: 300 ft (100 m) transmission radius
Quick and easy receiver frequency matching
TQG connection for use with Shure lavalier, headset, earset and instrument microphones and guitar cables
Easily accessible On / Off switch

Warranty:  2 years.