3.5mm Stereo Headset Hands-free Adapter/ Adaptor with Microphone and Control Button for Apple iPhone 4/ 3GS/ 3G S/ 3G, iTouch iPod Touch I II II IV 1 2 3 4 2nd 3rd 4th Generation Switch MP3 stereo hands-free to cell phone hands-free, you can enjoy MP3 stereo music as well as use MP3 hands-free as a cell phone handsfree With Micphone, add speak function to MP3 stereo hands-free Switch button, switch from music audio both ears to Mono single ear Mute switch, shut down micphone for listening function only Volume control, control volume online when switch between MP3 and cellphone