... .77 inch(external diameter 45mm) magnetic resistant 4 OhmsU Disk,SD/MMC Card Line in:configure 3.5mm stereo's plugs ... ,U Disk,SD/MMC CardPower supply:Outset Litheium battery,5V/1000mA AC ADAPTER ... -5VBattery capacity:500mAh Built-in MP3 player that can play SD / MMC memory card MP3 player music files, also read U diskremote ...