For noise levels up to 105 dBA, these behind-the-head earmuffs feature double-shell technology to provide effective hearing protection- Patented Twin-Cup™ design has soft, foam-filled earmuff cushions.- Behind the head design allows for easy use with hard hats.- Liquid/foam filled earmuff cushions.- Color-coding for compliance sighting.- Noise Reduction Rating (NRR)*: 29 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.3M is Leading the Advancement of Hearing Conservation™.