Product DescriptionThe Stanley Sync Stereo Earmuff with MP3 Connection delivers strong hearing protection and also lets you connect to a personal audio device. There s no knobs or controls to distract the wearer and no batteries are required. Audio performance is top notch with enhanced bass sounds. Suitable for most jobsites and work areas this lightweight earmuff features patented Air Flow Control technology for optimal attenuation across all frequencies. Whether you’re working indoors or out you’ll enjoy comfort and safety thanks to a slim earcup design and padded headband with reinforced fork slides. Noise Reduction Rating of 25.From the ManufacturerThe Stanley Sync Stereo Hearing Protector with MP3 Connection for use with MP3 players mobile phones and other personal listening devices offers acclaimed high-fidelity sound quality which is on par with professional headphones. A technologically advanced acoustical bass chamber (patent pending) enhances bass sounds that are typically sacrificed in a stereo earmuff; while its patented Volume Management Technology manages sound levels reaching the user s ear to a safe level providing a Noise Reduction Rating (NRR) 25. No batteries are needed as power volume and song selection are controlled from the personal listening device. Product includes a 3.5mm input cable to connect to most personal listening devices.