This is an OEM Black Headphone Jack Audio Flex for iPhone 4,which including the headphone jack ,the upper microphone and electronic portions of the volume buttons and silent switch
Perfect replacement part if you cann't hear anthing after you plug the headphone in you iPhone 4
http://www.hytparts.com/000396-new-oem-headphone-audio-jack-w-volume-switch-flex-cable-repair-part-for-iphone-4-black.html