Digital MP3/AM/FM Stereo Hearing Protector, Balance Comfort, Protection and The Ability To Listen To The Radio Or MP3 Player, Features Include: Noise Reduction Rating Of 21dB, Meets ANSI S319-1974 and CSA Z94.2-02, Class B, Retains 82dB Safe Noise Cut Off, Even With MP3 Player In Use, Automatic Radio Shut Off When MP3 Is Connected, Free Auxiliary Cord and 2 Heavy Duty "AA" Batteries.