E-44C Acoustic Tube Listen Only Earpiece is concealable, lightweight and comes complete with rubber eartips for all day comfort and enhanced acoustical engineering for a higher level of situational awareness. The Acoustic tube is designed with a threaded tube release to reduce moisture build-up in hot & humid climates. The shorter clear tube helps to prevent tube blockage. Please check your radio equipment carefully to select the correct audio jack size when ordering. 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.