The Surefire EP4 Sonic Defenders Plus protect your hearing without interfering with your ability to hear routine sounds or conversations. Their triple-flanged stem design fits larger ear canals and provides a Noise Reduction Rating (NRR) of 24dB. Sounds, at safe levels, are allowed to pass through into the ear canal, while potentially harmful noises (above 85dB) are reduced via a proprietary design that incorporates a special noise-reducing filter. EP4s include attached filter caps, which can be inserted for additional protection and blocking out lower-level noise, like that heard on a plane, where hearing ambient sounds or conversations isn't critical. Right/left color-coded Sonic Defenders Plus are made from a soft but durable, hypoallergenic polymer that provides all-day comfort and an extended product life (up to 6+ months, depending on usage and care)..