Input sensitivity: 500mV Output Power: 2W*28(OHM) 10% TDH Speaker: 1.25inch*4, 4(OHM) 3W, iron frame and built-in speaker Function: Vol+ Vol- Control, Power, Swithch AA Size Battery Out-link Power Compliant with earphone plus System Response: 60Hz-18KHz +/-3dB Dimension: 205*138*30mm Box size: 235*120*173mm Carton size: 745*250*366mm/12sets N.W.: 436g/set