Glasses ?ens of?Polaroid?from America company ?R 90 Flame ?hock proof and Anti-static electricity Audio ?ompatible formats: MP3/WAV/WMA ?tereo sound ?oice output power: 5MW+5MW ?oice output frequency: 20Hz-20Khz. Battery continuous playing time: 5 hours ?echarging time: 3 hours ?uilt-in lithium-ion polymer battery: 3.7V, 150mAh ?utomatically detected battery voltage and capacity ?uto power off Memory storage ?vailable flash memory size: 128MB/256MB/512MB/1G/2GB/4GB ?tandard USB 2.0 port ?ntegrated USB drive ?hare same USB port for download, upload and charge