USB Happy-Kid MP3 Player is not only a portable stereo speaker, but also a MP3 player. It has a built-in micro SD card slot which can read micro SD(HC) memory card for playing MP3/WMA audio files directly. It also allows connecting to iPods, MP3, MP4, MD, CD player, notebook, PC, PDA, PSP, mobile phone and other digital products with 3.5mm stereo audio connector. It has a built-in Lithium Ion battery - convenient to use.