Memory Flash: 512MB, 1 GB & 2GB Earphone impedance: 16 Ohms x 2 Voice output frequency: 20Hz-20Khz Voice output power: 55mW Maximum input power rating: 5VDC, 150mA Battery type/capacity: Built-in Lithium Ion Polymer/3.7v, 150mAh Charging Time: 3 hours Mfr. estimated battery life: 6 hours continuous Earphones type: Binaural Audio Additional features: Auto-power off Sound output mode: Stereo External hard drive function: Yes Playback Modes: Random play Signal-to-noise ratio: 87.2dB Digital formats supported: MP3/WAV/WMA PC interface supported: USB Colors: silver, black, white, red, yellow