3M™ Peltor™ Optime™ 105 Behind-the-Head earmuffs features low-profile ear cups that fit well with most helmets, Feature double-shell technology to effective hearing protection. The OPTIME 105 features added mass and volume, plus a unique “double-shell” earcup design (two cups connected via a foam inner layer to reduce structural resonances) to provide the maximum in noise reduction throughout the full range of low and high frequencies.