Caldwell E-Max Electronic Hearing Protection Standard profile E-Max hearing protection combines great circuitry with a standard earcup for better protection. Two microphones in the E-Max amplify sounds below 85 decibels which includes normal communication, range commands and environmental sounds. Above 85 decibels the microphones instantly shut off to protect the shooter's hearing. Two microphones - one in each cup - give the user true stereo sound and allow the user to identify the directional source of a sound. Runs on 2 AAA batteries (not included). 25 NRR.