Honeywell Sync Stereo Earmuff with MP3 Connection (RWS-53011) Connect to MP3 players, mobile phones and other personal listening devices via AUX input jack can (cable included); no volume knobs or power switches Technologically advanced acoustical bass chamber enhances bass sounds that are typically absent in stereo earmuffs Reduced sound across all frequencies via Patented Air Flow Control technology (without increasing earcup size or weight) Padded headband with reinforced fork slides and lightweight earcup design provide comfortable all-day wear No batteries required; Noise Reduction Rating (NRR) 25