MP3 Stereo 3.5mm Headset Audio Adapter w/Mic for SAMSUNG T219, T329, U420 Nimbus, Helio Drift, Heat, T509, R510, T519 Trace, Blackjack i607, M610, Upstage M620, T629, A717, A727, SYNC A707, U540, U740, D807, T809, D820, D900 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