Impact™ Sport Earmuff Noise Reduction Rating (NRR) 22. Employs built-in microphones amplify sounds and block hazardous noise . Users enjoy full, clear directional sound in stereo . Automatically shuts off amplification whenever harmful sound levels are reached (higher than 82dB) . Equipped with an external input and connection cord that allows you to connect to your own audio source . Battery life of up to 350 hours; Automatic shut-off after 4 hours to preserve battery life; Includes 2 AAA batteries R-01526