Peltor Sport RangeGuard Electronic Hearing Protector suppresses gunshot noise to protect hearing while amplifying voices for clear communication. Ideal for range and hunting use. Noise reduction rating (NRR) equal to 21 decibels. Low profile cup design works with shotguns & rifles. Single, external battery door. Adjustable padded headband. Durable recessed microphones. Features and Specifications NRR 21 dB Ideal for both indoor and outdoor shooters and hunters Suppresses gunshot noise to protect hearing while amplifying voices for clear communication Low profile cup design proven to work with shotguns & rifles Re-engineered headband for improved fit and comfort 4-hour auto shut-off Easy-access battery door with tether (Runs on 2 AAA batteries) 3.5 mm audio input jack compatible with most MP3 players and 2-way radios Durable recessed microphones