... 5. USB/SD card player 12" outdoor active subwoofer speaker box Portable PA System Features:1. USB/SD/MMC ... 12V external Rechargeable Battery 12V/7Ah Lead Acid Battery Frame Material PP ,MetalSpecial Designs ·Automatic Charge Design ·Battery ... *Room, outside(especially suitable dancing, gymnastics, demonstration's loud-speaker, recorded, play) *Teaching, Conference, classroom, military training, guide ...