E-42C is a professional grade listen only kit for use on brand speaker microphones. The clear quick disconnect acoustic tube provides for discreet operation and allows for easier exchange of ear pieces. Used by thousands of law enforcement officers, security companies, casinos, retailers and more! Available for 2.5mm, 3.5mm, 3.5mm threaded audio jacks. Please check your radio equipment carefully to select the correct audio jack size when ordering.