The ER-4P MicroPro noise-blocking earphones from Etymotic Research offer realistic sound reproduction and noise isolation that far surpasses that of active noise-canceling earphones. The ER-4P earphones--which require no batteries--can be plugged into any audio source. They can be used with portable CD, MP3, DVD, and other players without an additional amplifier. The ER-4P earphones were designed to match the response of the ear, creating nearly perfect sound reproduction. They reduce external sound naturally by sealing your ear canals, without the added weight, bulk, or external power supply required for active noise-canceling. Their external noise exclusion (up to 33 dB using the supplied 3-flange eartips and 41 dB with foam eartips) lets you hear the full dynamic range of recordings without your having to play them at unnaturally high and unsafe levels. What's in the Box: ER-4P MicroPro earphones, a 5-foot cord with 3.5 mm stereo phone plug, a .25-inch stereo phone adapter plug, six 3-flange eartips, 10 foam eartips, a filter-changing tool, 4 replacement filters, a shirt clip, a zippered pouch, a storage box, a user's manual, and warranty information.