HearDefenders-DF® dual-filtered hearing protectors feature Variable Attenuation. As noise levels go up, noise suppression goes up, allowing speech and radio communications to be heard!
HearDefenders-DF® are the first and only product to offer the flexibility of two levels of hearing protection and the ability to hook up to radio communications. They are specifically designed to help the user hear critical acoustics (sounds) including speech, while filtering out loud or harmful impact sounds.
If unsure between two sizes, go with the smaller size.