ELVEX Mil-Spec Electronic Hearing ProtectorsSeparate Mics, Separate Controls, Separate Batteries... Mil Spec Redundency! These ELVEX COM-550 electronic ear muffs block noise while amplifying sound. Superior 25 dB Noise Reduction Rating (NRR) is achieved with the deep ear cups and their dense foam lining. A separate microphone for each ear transmits stereophonic , directional sound. You can increase or decrease the sound in each ear with separate on/off and volume controls... You can hear a deer in the woods and even tell which direction he's coming from! Note: The electronic sound that you hear is limited to 82 dB for hearing protection. Mil-Spec Redundency - Having each earcup equipped with independent circuitry, contols, and batteries means that if one side fails (ie. dead batteries), the other side still works (A 4 hour auto-off feature saves on batteries). Of course the deep foam earcups will always block impulse (gunshot) noise. Convenience Features - CM-550 Muffs fold up for convenient storage in the carrying case (included). The battery compartments are easily accessible thru external coin slot screw compartments. They take 4 AAA batteries, two per side... And the Batteries Are Included, so there's nothing more to buy. 3.5mm Sound Input Jack - The left ear cup has an independent sound jack for plugging in a speaker wire. This can be for range or radio commands... Or for listening to anything (music, etc) that can feed in through a 3.5mm sound jack.