CAUTIONS: Although hearing protectors can be recommended for protection against the harmful effects of impulsive noise, the noise reduction rating (NRR)is based on attentuation of continuous noise, and may not be an accurate indicator of the protection attainable against impulsive noise, such as gunfire." Firing range instructors and frequent shooters, with more than 100 rounds in an eight-hour day, should use ear plugs in addition to the device to which this instruction sheet is attached, for maximum hearing protection.