For RealWear Navigator 500 series, HMT-1 and HMT 1-Z1 Designed to minimize audible wind noise in the RealWear Navigator 500 Series, HMT-1 and HMT-1Z1. Reduces low frequency bass, often described as rumble. Helps to improve the clarity of the recording, accuracy of the voice recognition system in windy environments, thereby extending functionality into more environments.