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 fitting directions 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. Constant or repetitive exposure to impulsive noise may lead to serious injury, temporary or permanent deafness. The noise reduction (NRR) calculated from the attenuation data is 33dB. Earplugs must be properly fitted to attenuate noise effectively. Refer to instructions. Improper fitting will reduce effectiveness and could result in hearing loss or injury. Keep away from infants and small children. These earplugs are nontoxic but may interfere with breathing if caught in windpipe, which could lead to serious injury or death.