The X-Series earmuffs are 3M’s latest advancement in hearing conservation. New technologies in comfort, design and protection all come together in this groundbreaking earmuff line. The X4A utilizes a newly designed spacer, specially formulated foam liners and innovative ear cushions to help improve attenuation. This lightweight, lower-profile earmuff helps with compatibility with other personal protective equipment and is designed for protection against moderate-to-high level industrial noise and other loud sounds. (bul)Replaceable ear cushions and foam liners. (bul)Noise Reduction Rating (NRR)b 27 dB. CSA Class AL. The NRR may overestimate the hearing protection provided during typical use. 3M recommends reducing the NRR by 50% for estimating the amount of noise reduction provided. Hearing Protection Solutions Made Innovatively Easy.