Feature:Air duct design principle、 is to prevent electromagnetic radiation. Sound through the air duct、 filter out the voice of the volume which is too strong and endanger human body health. So this one is no like other headphone wiht so loud sound. Long time wearing more comfortable、 ear won't pain、 and not easy to fall off. SpeakerSize: 15mmSensitivity: 102dB ¡À 2dB @ 1KzImpedance: 32¦¸Power: 10mWConnector:Life time:20000times(put in an take out)According to radio models、different connector availableMic:Dimension:6.0 x 5.0 mmSensitivity: -38dbImpedance: 2.2KRalated current: 100mAhMatching walkie-talkie type:Kenwood TH272G/372G、TK3130ProTalkSeries、TK313Free Talk series、BF-5118¡¢BF-5118A¡¢BF-5180¡¢BF6200¡¢BF6800 TK-3107¡¢TK-3207¡¢TK-2107¡¢TK-2207¡¢TK-308¡¢TK-208¡¢TK-3118¡¢TK-2118 ¡­etcPackage include:1 x Headsert Earphone1 x XSSML