Electronic ear defenders protect the ears against noise levels higher than 80dB.Solid state circuitry allows normal speech and sounds to be heard but automatically deadens any noise above 80dB.On/Off switch with adjustable volume control.Auto-adjust head band.Uses 2 x AA batteries (not included) providing approx. 200 hours of use.Conforms to EN352-1 H=34 M=31 L=24 SNR=26dB