Max support 4GB SD card/ U disk PlayMP3 audio formats Built in rechargeable Li-ion battery Double speakers 1, max support 4GB SD Card / U Disk2, Speaker: 4Ω 3W*23, with 3.5mm standard interface connector4. Built-in 600MA rechargeable lithium battery5, SNR: ≥85dB Audio: 150~18KHZ6. can work continuously 2-3 hours7. Double speakers8, Power input: 5V output: 3.7V 800MA