HEADPHONE FOR MP3/MP4/PMP PLAYERS. 2.5mm and 3.5mm AND MP3/MP4 WATCHES. if you order this headphone for your MP3/MP4 Watches, please leave a note, provide your MP3/MP4 watches model number,(which you can find from our website, the MP3/MP4 headphones will only compatiable with the MP3/MP4 watches purchased from our website.)