Koss QZ-77 Active Noise Reduction Ear Plug System Reduces harmful and annoying low frequency sounds in noisy environments Specialty ear cushion material forms slowly in ear canal providing a custom fit and maximum isolation Dynamic stereo phone element for extended frequency response (10 - 20,000Hz) Reduces harmful and annoying low frequency sounds in noisy environments Specialty ear cushion material forms slowly in ear canal providing a custom fit and maximum isolation Dynamic stereophone element for extended frequency response (10 - 20,000Hz) Compact design for convenient travel and portability Ideal for in-flight use