! ! !?SAFETY WARNING?: Be sure to write down the password,PIN code... that you have set,otherwise you will not be able to access the device!!. ! ! !?Missing or Upgrading APP?: Please contact the Luoran Team and we will provide you with the APK and installation steps, which are also very simple. Thank you very much for your letter. We will reply within 12 hours!. Expandable up to 256GB ?-This digital audio player provides a Micro SD card slot. It allows you to expand external storage up to 256GB and is compatible with SDXC, SDHC. This can greatly satisfy your need to store more songs, videos, audiobooks. Kids MP3 Player?-M4B is a music player for children, easy to set up parental controls. The digital player does not allow the installation of additional apps, which prevents children from installing inappropriate apps. Additionally, you can uninstall pre-installed apps(include browser)that you don't want your kids to use. Long Battery Life?-Built-in 1500mAh capacity battery with USB-C charging port. 2 hours full charge VS 50 hours music playing time, with standby power-saving feature. Wider Bluetooth Compatibility?-The device comes with a Bluetooth 5.0 chip, which can be backward or upward compatible with other versions of Bluetooth devices, such as headphones, speakers, car stereos, and provides fast pairing and stable connections. It is an excellent mp3 player with Bluetooth. ?Smart Music Player?-The device comes pre-installed with many of the most popular Spotify kids,Spotify, Music,HiBy Music and AIMP music. it is compatible with most music formats, including but not limited to MP3, WAV, FLAC, APE, OGG, M4A, AAC, WMA, MP2, etc., and provides various song categories, such as Title, Folder, Artist, Album.