Your hearing health should never be overlooked. SureFire EP4 Sonic Defender Plus safeguards your hearing against Noise-Induced Hearing Loss (NIHL) without sacrificing your ability to hear everyday sounds or conversations in noisy settings. Its triple-flanged stem offers a Noise Reduction Rating (NRR) of 24 dB. Safe sound levels can pass into the ear canal, while potentially damaging noises (above 85 dB) are reduced through their proprietary noise-reducing filter. EP4s come with attached filter caps that can be added for extra protection, blocking out lower-level noise, such as that on an airplane, where hearing ambient sounds or conversations isn't essential. Sonic Defenders are made from a soft, durable, hypoallergenic polymer that provides all-day comfort and can last over six months, depending on how they are used and cared for.