For noise levels up to 105 dBA, these behind-the-head earmuffs feature double-shell technology to provide effective hearing protection - Patented Twin-Cup(TM) 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™.