... :80hz-18khzDistortion :15%Loud speaker size: 50mmSNR:90dbSpeaker impedance :4ΩBattery capacity: 400mAHBattery impedance:400mΩMax SPL:30Colors:silver/brown/yellow ... MP3 , TF card, USB2.0, headphones output , AUX input external audio ♦External rechargeable battery ♦ Volume controlColor ---- Red, Blue, GREEN, Yellow ♦ MP3 format decoder ...