Some frequencies require FCC or Industry Canada license. Stop complicating communications. Simplify them with the PowerCom Plus II Radio Headset from Peltor. For more information on the smarter way in two-way visit call 1-800-225-9038 or e-mail peltor_communications@aearo.com OCTAVE BAND ATTENUATION DATA (dB) - ANSI S3.19 TEST DATA Model NRR CSA Class: Freq 125 250 500 1000 2000 3150 4000 6300 8000 MT53H7A4720 Headband model 25 dB B Mean sd 18.6 4.3 23.6 3.1 31.8 2.8 36.6 2.2 31.2 2.4 36.4