1.Specially designed for iPod nano charging Built-In high capacity Li battery, for iPod charging and also for mp3 & cell phone. 2.Audio portable system Golden finger setup in the bottom, playing beautiful music with MINI speaker. 3.FM transmitter, 2 frequency for choosing Transmit the music of Nano or other mp3 player. 4.Safety and reliability charging Charging through PC USB or power adapter and with management IC controls, charges fast and safely. 5. High efficient power convert High efficient voltage converting, raise the voltage of Li battery from 3.7v up to 5V , efficiency up to 85%.