3M Peltor Optime 95 Cap-Mount Earmuffs feature a universal mounting attachment that fits most hard hats. 3M Peltor Optime 95 cap-mount earmuffs feature a universal mounting attachment that fits most hard hats. For noise levels up to 95 dBA.Noise Reduction Rating (NRR)*: 21 dB. CSA Class B.*The NRR may overestimate the hearing protection provided during typical use. 3M recommends reducing the NRR according to the authority in your juristiction or reduce by 50-Percent for estimating the amount of noise reduction provided. The Peltor Optime 95 earmuff is recommended for very high noise level environments. Safe, comfortable and economical for all day protection. Note, this is the helmet attachment model.