The Elvex UltraSonic earmuff is the newest high performance earmuff with a Noise Reduction Rating of 29 dB. This earmuff has been designed to provide excellent full spectrum attenuation, as well as superb low frequency attenuation. Ultrasonic uses a fork style headband for even distribution of the pressure, and improved balance required for extra deep ear cups. The steel headband tolerates temperature extremes while the extra wide ear cushions provide the highest comfort. You get the ultimate performance and comfort with this muff! 29 dB NRR from certified US laboratory ANSI S3.19-1974. 34 dB SNR as tested by certified European laboratory to CE EN-352-1.