E-39C listen only earpiece is a great accessory for additional privacy, stealth communications, or for use in loud environments. Its clear acoustic coil tube wraps discreetly behind the ear, and the clear mushroom tipped earpiece hides inside the ear canal securely. 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.