HM Series headset microphone is ideally suited for vocal sound and speech application which  requires much freedom of movement.Especially the smallest size (the smallest capsule diameter of just 3.0mm)and lightest weight are ideal for application requiring minimum  visibility. Such as dance and sports instructors;Great for video use , this mini microphone is practically invisible.     

Direct connection Type(D  series)         HM-21S1/2/3/4/5/6    
L1   Standard 2.5mm single  plug           
L2   Standard 3.5mm stereo plug       
L3   Special thread  type 3.5mm plug       
L4   Sennheiser type 3.5mm stereo plug       
L5   AKG type 3-pin mini XLR       
L6   Shure type 4-pin XLR       
L7   Audio-technica  type 4-pin  mini XLR       
L8   Special usb plug        

HM-21S1/2/3/4/5/6   
Element:Back Electret Condenser        
Polar Pattern:Omni/Omni/Omni/Uni/Uni/Uni-directional       
Frequency Response:20Hz- 20KHz /20Hz- 20KHz /20Hz-20KHz  
                                                50Hz- 16KHz /50Hz- 16KHz /50Hz-16KHz      
Sensitivity:-44dB± 3dB /-44dB± 3dB /-46dB± 3dB      
Output Impedance:1.8K/2K/2K/1K/1K/1KΩ± 30%        
Max.Input SPL:130dB        
S/N Ratio:>70dB        
Power Supply:1.5V-10V        
Cable:Φ1.5*1.2M        
Dimension:Φ3.5/Φ5 /Φ5/Φ7/Φ7/Φ7mm       
Color:Black, Skin or other        
Accessories:Windscreen