Hearos Ear Plugs Rock 'n Roll Series Description: EASY to INSERT!Reusable and WashableNRR 22Free Case! For noise environments dominated by frequencies below 500 Hz, the C-weighted environmental noise level should be used. Improper fit of this device will reduce its effectiveness in attenuating noise. Consult the above instructions for proper fit. Although hearing protectors can be recommended for protection against the harmful effects of impulsive noise, the Noise Reduction Rating (NRR) is based on the attenuation of continuous noise and may not be an accurate indicator of the protection attainable against impulsive noise such as gunfire. The Noise Reduction Rating...